BERKELf Y 

LIBRARY 

owvERSHY  or 

CAUfO«WIA    . 


fntm    TMl   0*TOMIT«IC   LiailARY 
Of        

MONROE    JEROME    HIRSCH 


A' V3 


THE  LIBRARY 

OF 

THE  UNIVERSITY 

OE  CALIEORNIA 


GIVEN  WITH  LOVE  TO  THE 

OPTOMETRY  LIBRARY 

BY 

MONROE  I.  HIRSCH,  O.D.,  Ph.D. 


CLASSIFICATON 

OF   THE 

Motor  Anomalies  of  the  Eye 

BASED    UPON    PHYSIOLOGICAL   PRINCIPLES 
TOGETHER   WITH   THEIR 

SYMPTOMS,    DIAGNOSIS   AND   TREATMENT 


ALEXANDER  DUANE,   M.D. 

ASSISTANT  SURGEON   OPHTHALMIC  AND  AURAL  INSTITUTE,  NEW    YOFK 


Nbw  York 

WILLIAM   R.  JENKINS   CO. 

PUBLISHERS 

851-853  Sixth  Avenue 
1910 


(a 

OPTOMETRY 


PREFACE, 


The  following  brochure  respresents  the  result  of  some 
ten  years'  labor  and- study  expended  upon  the  subject  of 
muscular  anomalies.  Whatever  merit  it  may  have  is  due 
to  the  fact  that  it  stands  for  original  investigation  in  a  field 
still  full  of  difficulties  and  obscurities.  The  author's 
clinical  experience  has  convinced  him  that  the  classifica- 
tions propounded  furnishes  an  adequate  working  basis  for 
the  diagnosis  of  these  conditions.  And  his  experience  as 
a  teacher  at  the  Ophthalmic  and  Aural  Institue  has  led 
him  to  believe  that  the  principles  here  laid  down,  and  the 
means  and  methods  of  examination  here  recommended, 
have  been  found  by  others  also  to  be  both  intelligible  and 
practicable.  Many  of  these  principles  and  methods  have 
been  enunciated  in  lectures  given  to  successive  classes  of 
practitioners,  and  have  been  demonstrated  in  their  prac- 
tical application  upon  patients  before  the  same  gentlemen ; 
the  auhor's  constant  attempt  being  to  present  clearly  and 
in  a  way  suited  to  general  comprehension  the  rules  for  the 
diagnosis  and  management  of  the  muscular  anomalies. 
That  this  attempt  was  not  unsuccessful  he  has  had  some 
reason  to  believe  from  the  assurances  of  those  that  he  has 
taught;  and  it  is,  therefore,  with  th-  hope  that  the  result 
of  his  work  may  be  useful  to  others  as  well  that  he  now 
offers  it  to  the  public. 

Alexander  Duane,  M.  D. 

4ii  East  Thirtieth  tit..  New  I'orh. 
April  'jy,  1S97. 


EBBATUM. 

Page  23,  line  11:     For  •'•-!2,"  read  -'L^'/:." 


Reprinted  from  Annals  of  Ophthalmology  and  Otology,  October, 


A  NEW  CLASSIFICATION  OF  THE  MOTOR  ANOMA- 
LIES OF  THE  EYE,  BASED  UPON  PHYSIO- 
LOGICAL PRINCIPLES. 

THE  PRIZE  ESSAY  OF  THE    ALUMNI    ASSOCIATION  OF  THE  COLLEGE  OF  I'llY- 
SICIANS  AND  SURGEONS,  NEW  YORK,  FOR  1S96. 

By  Alexander  Duane,  M.  D., 

NEW    YORK. 

ILLUSTRATED. 

Introduction. — Sketch  of  previous  classiflcatious. — Development  of 
the  idea  of  an  etiological^  as  opposed  to  a  simple  anatomical  classiti- 
cation. 

I.  Nature  of  the  problems  that  have  to  be  solved  in  under- 
taking a  physiological  classitication. 

II.  The  Movements  of  the  Normal  Eye. — Actions  of  the  indi- 
vidual muscles. — Movements  of  eacii  eye  individually  and  the  mus- 
cles by  which  they  are  performed. — Amount  of  these  movements. — 
Field  of  tixatiou. — Author's  experiments. — Power  of  the  individual 
muscles. — Coordinated  movements  of  the  two  eyes. — Table  of  asso- 
ciated parallel  movements  and  the  muscles  producing  them. — Asso- 
ciated antagonists. — Field  of  binocular  single  vision  and  of  binocular 
fixation. — Author's  experiments. — Movements  of  convergence. — 
Power  of  convergence. — Convergence  near-point. — Prism-conver- 
gence.— Movements  of  divergence. — Nature  of  divergence  action. — 
Movements  of  sursumvergence. — Rotation  movements.  —  Ap- 
pendix.— Diagrammatic  representation  of  the  movements  of  the  eye. 

III.  The  Tests  Employed  and  Their  Significance.— Object  of  the 

tests. — Tests  for  l)inocular  distant  fixation. — Inspection. — Fixation 
and  diplopia  tests. — Equilibrium  tests  — Screen  test. — Parallax  test. — 
Tests  for  associated  parallel  movements. — Tests  for  convergence. — 
Tests  for  divergence. — Tests  for  sursumvergence. — Way  in  which 
the  tests  are  applied  in  practice. 

INTRODUCTION. 

The  nomenclature  and  classification  of  the  muscular  anomalies 
of  the  eye  have  been  passing  through  the  same  stages  that  have 
been  noted  in  the  evolution  of  the  nosology  of  other  parts  of  the 
body.     In  the  progress  of  our  knowledge  in  regard  to  any  given 


2  XKW  CLASSIFICATION  OF   MOTOK   ANOMALIES. 

set  of  ailments,  the  first  classification  has  always  been  based  upon 
that  which  first  strikes  the  eye  of  the  observer,  namely,  the  out- 
ward appearances  and  symptoms.  Thus,  many  cases  of  renal  dis- 
ease were  first  classified  as  drbpsy,  and  dropsy  formerly  figured 
among  physicians,  as  it  does  still  among  the  laity,  as  a  substantive 
disease,  and  to  be  treated  as  such.  But,  as  medical  science  pro- 
gressed, and  the  underlying  causes  of  disease  were  more  and 
more  brought  to  light,  it  became  evident  that  dropsy  is  a  symp- 
tom only  and  to  be  treated  as  a  symptom,  and  that  the  principles 
of  a  rational  pathology  require  us  to  search  for  the  causes  of  the 
dropsy  and  to  institute  treatment  addressed  to  the  removal  of 
these  causes  rather  than  to  the  direct  relief  oi  the  dropsy  itself. 
In  this  way  a  pathological  classification  is  gradually  substituted 
for  one  that  is  purely  symptomatic,  and  a  scientific,  casual  treat- 
ment for  one  that  is  empirical,  or  based  solely  on  the.  appearances 
presented. 

This  conception  of  disease  as  a  symptom  of  a  pathological  pro- 
cess, and  the  consequent  conviction  that  our  therapeusis  must 
be  based  ultimately  upon  an  etiological  foundation,  could  not 
have  developed,  or  at  all  events,  could  not  have  become  anything 
more  than  a  plausible  theory,  barren  of  practical  application,  were 
it  not  constantly  fortified  by  a  steady  increase  in  the  number  and 
precision  of  our  means  of  diagnosis.  In  this  way  only  can  we 
make  those  fine  discriminations  between  symptoms  that  enable 
us  to  form  accurate  inferences  as  to  the  diverse  origin  of  phenom- 
ena which,  to  a  cursory  observation,  seem  identical.  For  exam- 
ple, our  knowledge  of  the  symptomatic  nature  of  dropsy  and  of 
the  necessity  of  treating  it  from  an  etiological  standpoint,  how- 
ever true  it  might  be,  would  be  a  theory  only,  unprovable  and 
practically  inapplicable,  were  it  not  for  the  refijied  means  we  now 
possess  for  examining  the  chest  and  abdomen  and  for  analyzing 
the  urine.  These  diagnostic  means  have  enabled  us  to  convert 
theory  into  fact,  and  to  redeem  our  treatment  from  the  charge 
of  empiricism. 

A  similar  process  of  evolution  has  taken  place  in  regard  to  the 
motor  anomalies  of  the  eye.  These  were  formerly  (and  to  a 
great  extent  still  are)  classified  simply  according  to  the  appear- 
ances presented,  i.  e.,  as  inward,  outward,  upward,  or  downward 
deviations.  And.  to  recur  to  our  former  illustration,  just  as 
dropsy  usc<l  to  be  treated  as  dropsy,  regardless  of  whether  it  was 
due  to  renal,  cardiac,  or  hepatic  disease,  so  an  inward  squint  was 
(ami  often  still  is)  treated  simply,  as  a  squint,  quite  without 
reference  to  its  origin.  The  results  in  both  cases  have  often  been 
disappointing. 


NEW  CLASSIFICATION  OF  MOTOR  ANOMALIES.  6 

The  first  great  step  in  advance  was  taken  by  Donders,  when 
he  demonstrated  the  frequent  connection  and  apparent  causal  re- 
lation between  strabismus  convergens  and  hypermetropia,  and 
between  strabismus  divergens  and  myopia.  And,  while  subse- 
quent writers  have  doubtless  gone  too  far  in  asserting  the  univer- 
sal application  of  his  deductions,  the  service  that  he  himself  did 
to  rational  therapeutics  by  indicating  one  large  class  of  cases 
in  which  a  strictly  causal  treatment  relieves  the  symptoms,  can 
scarcely  be  overestimated. 

Another  exceedingly  important  advance  made  was  in  the  dis- 
covery of  the  insufficiencies  and  of  the  methods  of  estimating 
them.  These  latter,  devised  by  V.  Graefe,  remain  to-day  among 
the  chief  means  of  discriminating  between  the  various  motor 
anomalies;  and  their  invention,  as  in  the  case  of  all  new  methods 
of  precision,  opened  the  way  to  still  further  discoveries. 

The  diagnosis  ajid  symptomatology  of  paralytic  deviations  was 
also  worked  out  by  the  same  author,  and  in  a  manner  so  admira- 
bly complete,  that  little  remained  for  his  successors  to  do  ex- 
cept to  gather  statistics  in  regard  to  the  precise  etiology  of  these 
interesting  affections. 

V.  Graefe  had  pointed  out  the  relation  between  insufficiency 
and  squint,  but  since  his  time  this  relation  has  been  largely  over- 
looked, the  consequence  being  that  the  two  conditions  have  of- 
ten been  classed  as  categorically  distinct,  and  distinct  principles 
of  treatment  have  been  applied  to  them.  This  arbitrary  separa- 
tion of  two  things  really  the  same  has  had  a  retarding  influence 
upon  the  development  of  our  knowledge  of  muscular  anomalies. 

It  toecame,  after  awhile,  apparent  that  the  very  term  insuffi- 
ciency was  a  defective  one,  implying,  as  it  did,  a  casual  relation, 
which  was  by  no  means  always  present.  Hence,  Stevens  in  this 
country  proposed  a  system  of  classification  in  which  the  term  in- 
sufficiency was  replaced  by  Jiderophoria.  and  the  term  strabis- 
mus by  heterotrofia.  the  former  indicating  a  tendency  to  de- 
viation, which  tendency  is  habitually  overcome,  and  the  latter 
a  deviation  which  is  more  or  less  constantly  present. 
The  further  use  of  the  prefixes  Eso-,  Exo-,  and  Hyper-,  served 
to  differentiate  between  deviations  or  tendencies  inward  (con- 
vergent deviation),  outward  (divergent  deviation),  and  upward 
for,  more  properly,  divergence  in  a  vertical  plane).  This  classi- 
fication is  extremely  convenient  and  has  been  generally  accepted, 
at  least  in  America.  Furthermore,  the  instruments  of  precision, 
which  the  same  author  devised  for  measuring  the  various  devia- 
tions, are  doubtless  the  best  extant,  and  have  greatly  facilitated 
the  recognition  and  differentiation  of  the  anomalies  in  question. 


4  NEW  CLASSII-ICATION  OF  MOTOR  ANOMALIES. 

Stevens  also  did  sen^ice  in  pointing  out  that  many  cases  of  so- 
called  insufficiency,  or  heterophoria,  were  really  low  degrees  of 
squint — a  fact  which,  as  already  stated,  has  been  too  much  over- 
looked. 

He  further  called  particular  attention  to  the  importance  and 
frequency  of  the  vertical  deviations  which  had  received  (and,  in 
fact,  still  receive)  too  little  notice;  the  fact  being  that  their  recog- 
nition and  correction  are  very  necessary  features  in  the  manage- 
ment of  many  cases  of  muscular  trouble. 

Stevens'  classification,  however,  is  open  to  the  serious  objec- 
tion that  it  reinstates  the  idea  of  grouping  deviations  according 
to  their  anatomical  characters  and  puts  the  etiological  element 
in  the  background.  Tliat  is,  it  aims  to  classify  motor  disorders 
according  to  their  outward,  visible  characters,  and  not  according 
to  their  cause.  In  this  way,  though  admirable  in  other  respects, 
it  would  seem  to  be  a  distinct  step  backwards.  Thus,  while  the 
term  insufficiency  is  faulty,  because  it  restricts  too  narrowly  our 
conception  of  the  possible  etiology  of  a  given  motor  affection, 
the  term  heterophoria  is  objectionable,  because  it  throws  away 
the  etiological  idea  altogether,  and  once  more  directs  our  atten- 
tion simply  to  the  appearances  present,  i.  e.,  to  the  fact  that  the 
eye  in  a  certain  case  deviates  up,  down,  out,  or  in.  To  be  sure, 
this  has  its  advantages  in  that  there  are  many  cases  in  which  we 
cannot  say  at  once,  or  even  after  considerable  testing,  what  the 
true  condition  underlying  these  appearances  is,  and  we  have, 
therefore,  to  content  ourselves  with  a  provisional — i.  e.,  an  anat- 
omical— diagnosis.  But  we  should  always  feel  that  such  a  diag- 
nosis is  provisional,  and  that  a  really  satisfactory  diagnosis 
should  express  the  cause  of  the  deviation  as  well  as  its  char- 
acter. That  is,  the  statement  that  in  a  given  case  so  many  de- 
grees of  esophoria  were  found  should  be  regarded  as  only  an  in- 
complete presentation  of  the  facts;  the  final  diagnosis  not  being 
reached  until  we  have  determined  the  cause  of  the  esophoria,  i.  e., 
have  made  out  which  one  of  the  many  and  complex  functions 
of  the  neuro-muscular  apparatus  of  the  eye  is  deranged.  In  the 
meantime,  the  terms  that  Stevens  has  devised  are  very  conven- 
ient for  puri:)oscs  of  record  and  for  indicating  the  provisional  di- 
agnosis. 

The  next  step  naturally  left  to  take — the  classification,  namely, 
of  the  motor  affections  of  the  eye  upon  an  etiological  basis — has 
been  but  partially  made.  Apart  from  Bonder's  researches  be- 
fore mentioned,  and  V.  Graefe's  demonstrations  of  the  characters 


NEW  CLASSIFICATION  OF  MOTOR  ANOMALIES.  0 

displayed  by  paretic  squint,  the  main  contributions  to  the  sub- 
ject have  been  A.  Graefe's  description  of  convergence-insuffi- 
ciency, Landolt's  observations  upon  the  comparative  effect  and 
relative  value  of  advancement  and  tenotomy  in  the  treatment  of 
various  kinds  of  strabismus,  and  some  of  Stevens'  recent  papers. 
Nowhere,  however,  have  the  observations  bearing  upon  this 
point  been  properly  co-ordinated,  so  as  to  form  a  complete  classi- 
fication of  all  the  different  anomalies,  founded  upon  a  strictly  eti- 
ological and  physiological  basis.  To  do  this,  at  least  in  part,  is 
the  object  of  the  present  essay,  which  is  based  almost  exclusively 
upon  observations  made  by  the  author  himself  during  the  past 
ten  years.  The  subject  has  seemed  to  him  to  be  one  not  only  of 
scientific  interest,  but  also  of  great  practical  importance,  since, 
as  experience  has  shown,  our  plans  of  treatment  are  necessarily 
largely  modified  by  our  notions  of  the  real  nature  and  causes  of 
the  condition  that  we  are  called  upon  to  correct.  Moreover,  the 
cases  themselves  are  very  numerous;  their  symptoms,  subjective 
and  objective,  are  multiform  and  complex;  while  the  results  of 
treatment,  which  are  often  brilliant,  are  often  also  disappointing, 
owing,  no  doubt,  frequently,  to  our  ignorance  of  the  exact  na- 
ture of  the  case  before  us.  It  has  seemed  proper,  therefore,  to 
enter  into  considerable  detail  in  trying  to  determine  what  should 
be  the  proper  classification  of  such  cases,  and  what  precisely  are 
the  differential  marks  by  which  they  can  be  distinguished  one 
from  the  other. 

I. 

NATURE    OF    THE    PROBLEM. 

The  task  that  confronts  us  when  we  attempt  to  make  any  classi- 
fication of  the  kind  now  essayed  is  that  of  framing  a  scheme  by 
reference  to  which  the  following  problem  may,  in  most  instances, 
at  least,  be  resolved  :  Given  a  case  zutth  a  certain  train  of  symp- 
toms^ to  determine  the  ultimate  cause  of  these  symptoms^  i.  e., 
the  part  or  function  that  is  primarily  deranged^  and  the  manner 
of  its  derangement.  The  solution  of  this  problem  obviously  pre- 
supposes, first,  an  accurate  knowledge  of  the  normal  state  of  the 
various  parts  and  functions  that  may  be  involved,  and,  second, 
a  consideration  of  the  different  means  we  have  for  determining 
whether  each  part  or  function  is  actually  normal  or  not.  Thus, 
in  the  case  of  deformities  about  the  hip,  a  proper  classification,  i. 
e.,  one  which  tells  us  whether  any  given  deformity  is  due  to  a 
fracture,  to  a  dorsal  dislocation,  or  to  hip-disease,  is  possible  only 
after  we  have  become  thoroughly  acquainted  with  the  normal  re- 
lations and  movements  of  the  hip-joint,  and  with  the  means  at  our 


G  NEW  CLASSIFICATION-  OK   MOTOR  ANOMALIES. 

coinmand  for  appreciating  the  various  deviations  from  the  nor- 
mal and  their  significance.  Applying  this  principle  to  the  eye, 
^ve  may  say  that  the  solution  of  our  problem  is  contained  in  the 
answers  to  the  following  questions: 

(1).  What  are  the  different  normal  functions  of  the  neuro- 
muscular apparatus  of  the  eye,  and  what  is  their  anatomical 
seal? 

(2).  In  \\hat  way  is  it  possible  for  these  functions  to  be  de- 
ranged ? 

(3).  \Miat  means  have  \vc  for  telling  whether  any  special  func- 
tion is  deranged  or  not,  and,  if  so,  what  the  nature  of  the  derange- 
ment is? 

(4).  What  are  the  conditions  actually  met  wdth  in  practice, 
and  how  do  they  correspond  to  the  scheme  that  w-e  have  framed? 

The  consideration  of  these  questions  we  will  now  take  up  in  the 
order  named. 

II. 


MOVEMENTS  OF  THE  jSTOKMAL  EYE. 
The  functions  concerned  in  the  group  of  cases  under  consid- 
eration comprise  (a)  the  actions  of  the  individual  nntscles  that 
are  inserted  into  the  eyeball ;  (<5)  the  ?uovcments  possible  to  each 
eye  separately  through  the  individual  or  concerted  working  of 
these  muscles  and  (c),  the  character  and  extent  of  the  move- 
ments actually  performed  by  the  tzvo  eyes  when  acting  together. 

The    actions   of  the   individual   muscles   are   best  exhibited  in 
tabular  form,  as  follows: 


end 
ridi- 

(tor- 

i-s-: 

III 

0.2 

§s 

Field  of 

&ilps^ 

Hi 

> 

0  57 

■■Sg 

1.2-2 

Muscle 

action         1^2    s?  ^^ 

Lateral  a 
sional  eff. 
creasing  a 

I 

II 

*  "3.2  >> 

limited  to        >  ii 

llll 
Pi  o  « 

Lateral; 
effects 
ingto  Z( 
;    is 

it 

II 

External 

Outer  half  of  '  Out 

No  ac- 

No ac- 

Rectus. 

field  of  fixation} 

tion 

tion 

Internal 

Inner  half  of 

In 

No  ac- 

No ac- 

Rectus. 

field  of  fixation 

tion 

tion 

Superior 

Upper  half  of 

In 

in 

Adduct- 

Abduct- 

Up 

Abduct  - 

Ad- 

Rectus. 

field  of  fixation 

ed. 

ed. 

ed. 

ducted 

Inferior 

Lower  half  of     In 

Out 

Adduct- 

Abduct- 

Down 

Abduct- 

Ad- 

Rectus. 

field  of  fixation 

cd. 

ed. 

ed. 

ducted 

Superior 

Lower  half  of    Out 

In 

Ab.liut- 

.\(ld.K-l- 

Down 

Ail.luct- 

Ab- 

oblique 

field  of  fixation 

id. 

cd. 

td. 

ducted 

Inferior 

Upper  half  of    Out 

Out 

Abduct- 

Adduct- 

Up 

Adduct- 

Ab- 

Oblique 

field  of  fixation 

ed 

ed. 

ed. 

ducted 

NEW  CLASSIFICATION  OF   MOTOR  ANOMALIES.  < 

It  will  be  seen  from  the  foregoing  table  that,  under  ordinary 
conditions  the  only  two  muscles  which  precisely  counteract  one 
another's  action,  or  which  are,  in  the  language  of  physiology, 
direct  antagonists,  are  the  external  and  internal  recti. 

The  superior  and  inferior  recti,  for  example,  are  only  partially 
antagouistic,  for.  while  respectively  elevatiug  and  depressing  tlie 
eye,  so  as  to  be  directly  opposed  to  each  other  in  this  regard,  and 
while  'tlieir  action  in  rotating  the  vertical  meridian  of  the  cornea 
is  also  precisely  opposite,  they  both  adduet  the  eye.  Hence,  when 
acting  together  they  will  reinforce  the  internal  rectus,  and  this 
action  will  be  most  strongly  pronounced  Avhen  the  eye  is  already 
markedly  adducted,  i.  e.,  under  conditions  in  which  the  internal 
rectus  is  Avorking  at  some  mechanical  disadvantage.  The  like  is 
true  O'f  the  combined  action  of  the  two  obliques,  which  neutralize 
each  other  as  far  as  rotation  of  the  vertical  meridian  and  as  far 
as  elevation  and  depression  are  concerned,  but  work  'together  in  pro- 
ducing abduction  and  hence  assist  the  extei-nal  rectus,  especially 
Avheu  the  eye  is  already  strongly  abducted.  On  the  other  hand, 
when  the  eye  is  strongly  adducted,  the  lateral  action  of  the  two 
obliques  falls  away,  and  these  two  muscles  act  siimply  to  elevate  and 
depress  the  eye  respectively.  In  this  position,  therefore,  they  do 
neutralize  each  other  perfectly,  and  are  direct  antagonists.  The 
saime  is  true  of  the  superior  and  inferior  recti  when  the  eye  is  ab- 
ducted. For  further  remarks  upon  this  subject,  see  the  appendix 
to  this  chapter. 

Almost  every  movement  that  the  eye  can  make  requires  the 
combined  action  of  at  least  two  of  the  ocular  muscles.  Thus  to 
lift  the  eye  straight  upwards,  we  must  use  both  the  superior 
rectus  and  the  inferior  oblique. 

The  superior  rectus,  acting  by  itself,  would  carry  the  eye  inward 
as  well  as  upward,  and  would  rotate  the  vertical  meridian  of  the 
cornea  inward.  So,  too,  the  inferior  oblique,  acting  by  itself,  would 
tend  to  abduct  the  eye  and  rotate  the  vertical  meridian  outward. 
Neither,  therefore,  alone  will  carry  the  eye  straight  upward,  but 
the  two  acting  together,  will  neutralize  each  other  as  far  as  their 
lateral  working  and  their  effect  upon  the  vertical  meridian  are  con- 
cerned, and  consequently  the  eye  rises  vertically,  without  swerving 
to  the  right  or  left,  and  without  any  deflection  of  its  vertical 
meridian. 

It  is  probable  that  the  external  and  internal  recti  assist  in  main- 
taining the  strict  verticality  of  this  movement,  their  simultaneous 
contraction  steadying  the  eye  and  preventing  it  from  swerving.  In 
this  case,  therefore,  at  least  two,  and  probably  four  muscles,  are 
concerned  in  the  movement. 

Similarly,  depression  of  the  eye  is  always  accomplished  by  the 
conjoint  action  of  the  inferior  rectus  and  the  superior  oblique, 
which  neutralize  each  other  to  a  greater  or  less  extent,  as  far  as 
their  lateral  working  and  their  effect  upon  the  vertical  meridian 
are  concerned,  but  which  assist  each  other  in  carrying  the  eye 
downward.  Here.  too.  probably  the  external  and  internal  recti  come 
into  play  as  steadying  and  supporting  factors. 

Even  in  so  simple  a  movement  as  that  of  abduction,  which  might 
be  performed  by  a  single  muscle,  it  is  probable  that  at  least  two 


8  XK\V  CLASSIFICATION  OF   MOTOU   ANOMALIES. 

(i.  e..  both  obliques),  or  even  four  other  niuseles  (i.  e.,  all  except 
the  internus),  take  part  either  in  reinforcing  the  action,  or  in  steady- 
ing the  eye  and  rendering  the  movement  uniform.     8e<^  Appendix. 

The  nioveiiiciits  of  the  individual  ocular  muscles  are,  as  is  well 
known,  presided  over  by  more  or  less  discrete  nuclei  scattered 
along  the  walls  of  the  third  ventricle,  aqueduct  of  Sylvius,  and 
fourth  ventricle;  but  the  precise  method  in  w^hich  these  are  ar- 
ranged and  inter-connected  has  not  yet  been  sufficiently  deter- 
mined. 

The  Movements  Possible  to  the  Eye  through  the  co-ordi- 
nated action  of  its  six  muscles  comprise  rotations  in  every  con- 
ceivable plane,  the  eye  being  capable  of  moving  from  the  primary 
position  directly  to  any  secondary  position,  and  from  the  latter 
again  to  any  other  secondary  position,  and  in  so  doing  may  take 
either  a  direct  or  a  sinuous  course.*  The  typical  direct  move- 
ments from  the  primary  position,  together  with  the  muscles  con- 
cerned in  the  production  of  these  movements,  are  shown  in  the 
following  table : 

*This  may  be  proved  by  making  two  fine  dots  upon  a  card,  so 
close  together  that  unless  very  accurately  fixed  (i.  e.,  if  seen  ever  so 
slig"htly  in  diffusion  circles),  they  will  blend  into  one.  and  then  mov- 
ing the  card  slowly  in  all  directions  before  the  eye.  the  head  re- 
maining fixed.  However  the  card  is  moved,  the  two  dots  will  re- 
main distinct,  thus  showing  that  the  eye  follows  them  in  all  their 
movements. 


NEW  CLASSIFICATION  OF   MOTOR   ANOMALIES. 


0  o  S  P.  a 


(Abduc- 
tiou) 


(Adduc- 
tion.) 


Move  Eye 
Laterally* 


Syner- 
gists. 


Superior 
Oblique 


Inferior 
Oblique 


Oppo- 
nents. 


Superior 
Rectus. 


Inferior 
Rectus. 


Move      Eye 
Vertically* 


Rotate  Upper 
End  of  Verti- 
cal Meridan 
of  Cornea* 


No    action.  No  action, 


Out  1  Action 
I  increas 
I  ing  the! 
y  further 

Out  1  the  eye 
I  i.s  ab- 
J  ducted. 


Down]  1    Action 
I  equal 
I  and  op- 
posite; 
j-decreas 
[Up]       ing  the 
more 


[Out] 


the  eye 

I  ■ 


is  ab- 
ducted. 


[In] 


[In] 


"I  Actions 

I     slight  !    [UpJ 

I  and  de- 

!    creas- 

Hng  the 

I     more  I 

the  eye  [Down 
I  is      ab- 
J  ducted. 


]  Actions 
1  equal 
I  and  op- 
I  posite; 
1  increas 
[ing  the 
I  more 
I  the  eye 
I  is  ab- 
J  ducted. 


Ilnternal  ! 
I      Rectus 


Syner- 
gists.] 


Superior 
Rectus 


Inferior  I 
Rectus 


Oppo- 
nents. 


In 


Action 
increas- 
ing thel 
•  more  I 
the  eye 
is  ad- 
ducted. 


[In]   1  Actions 
I  equal 
and 
I oppo- 
'  site; 
increas 
ing  the 

I  the  eve 
I  is  ab- 
J  ducted. 
1  Actions 

equal 

and 
[In]    I  oppo- 
I  site; 
f decreas 
I  ing  the 
I  more 
[Out]  i  the  eye 
1  is      ab- 
j  ducted. 

No  action. 


Superior  j  [Out]  1  Action 
Oblique  I    slight 

!  I  and  di- 

minish- 


Inferior  j  fO"t] 
Oblique! 


"I  Action* 
[Up]  I  equal  [In] 
I  and  op- 
f  posite; 
f decreas 
;Down]  I  ing  as  [Out[ 
' the  eye 


Action 
equal     [In] 

and  op- 
posite; 

increas 


ing  as 
the  eye 
is  ad- 
ducted,  1 


[Up] 


mg  as 

the  eye  [Out] 
is  ad-  I 
ducted. ' 

I 


1  Actions 

equal 

I  and  op- 

I   posite;! 

'ncreas 


ducted. 


Actions 
equal 
and  op- 
posite: 
dimin- 
ishing 
as  eye 
is  ad- 
ducted. 


Resultant 

Effect  Upon 

Eye. 


Eye  carried 
out   mainly  by 
action  of  ex- 
ternal rectus 
assisted  by  the 
two  obliques ; 
the   effect   of 
the     latter  be- 
ing the  greater 
the  more  the 
eye  is   abduct- 
ed.    The  op- 
posing (ad- 
ducting)    ac- 
tion of   the  su- 
perior and   iu- 
ferior  recti 
also  dimin- 
ishes as  the 
eye  is   abduct- 
ed.    The  eye 
is  steadied 
and  its    verti 
cal  meridian 
kept  vertical 
by  the  traction 
exerted  by 
the   superior 
and    inferior 
recti    and    the 
two  obliques. 

Eye  carried  in 
mainly  by  in- 
ternal rectus, 
assisted  by  the 
superior  and 
inferior  recti: 
the  effect  of  the 
latter  being 
greater,  the 
more  the  aye 
is  adducted. 

The  opposing 
(abducting)ac- 
tion  of  the  two 
obliques  dim- 
inishes as  the 
eve  is  adduc- 
ted. The  eye 
is  steadied  and 
its  vertical  me- 
ridian kept 
vertical  by  the 
counterpois- 
ing action  of 
the  two  obli- 
ques and  the 
superior  and 
inferior    recti. 


*    Movements   that  are   completely   neutralized     by     the   action   of   opposi 
muscles  are  placed  in  brackets. 


10 


NEW  CLASSIFICATION  OK  MOTOH   ANOMALIES. 


•r «~  Vi  'C  O 

fi  o  Sb^ 

Up 
(SuTsum- 
duction) 


Muscles 

Con- 
cerned. 


Move    Eye 
Laterally 


Rotate    Upper  d       »»      » 

Move    Eye       ,End  of  Vertical  pS^^J^\^°' 

Vertically            Meridian  of  ^,uli}^^ 

Cornea         |  the  Eye 


Superior     [In]  1     Move-  Up. 

Rectus  ments    ■ 

Inferior  >    equal  ! 

Oblique  [Out]  I  and  op- Up. 
J    posite.i 

Syner-      I 
gists. 
External   [Out] 
,      Rectus 


[In] 


Diagon- 
ally Up 
and  Out. 


Internal 
Rectus 
Superior   [In] 

Rectus  slight  and  dim- 
inishing as  eye 
is  abducted. 


Actions  No  action 

equal 
and 

oppo-    No  action 
site^ ! 

Action 


[In]  1  Actions 
I  equal 
[andop- 

[Out[  J  posite. 


No  action 


Up,  Action  [In]  ;       Action, 

marked  and  in-  slight  and  dim- 
creasiug  as  eye  inishing  as  eye' 
bducted.  is  abducted. 


Inferior 
Oblique 


Out;  Action  Up;  Action  Out  :  Action 
increasing  as  slight  and  de-  marked  and  in- 
eye  is  abduc- creasing  as  eye  creasing  as  eye 
ted-  is  abducted.  is  abducted.       | 


Diagon- 
ally Up 
and  In. 


Superior  I     In:       Action      Up;      Actionl     In:        Action 

Rectus  increases        as  slight  and   de-  increases        as 

jeye    is   carried  creasing  as  eye  eye    is   carried 

linward.  is        adducted; 

finally  U. 


Inferior     [Out];     Action      Up;      Action      [Out]  Action 
Oblique  slight  and   de-  marked        and  slight   and   de- 
creasing as  eye  increasing     as'creasing  as  eye 
is  carried  in.       eye   is   carried  is  carried  in. 
in.  I 


Internal    In. 
Rectus. 


Eye  carried 
straight  up: 
vertical  meri- 
dian remains 
vertical.  The 
counterpois- 
ing actiou  of 
the  internal 
and  external 
recti  serves  to 
steady  eye  and 
keep  it  in  the 
vertical  line- 
Eye  carried 
up  mainly  by 
superior  rec- 
tus, the  elevat- 
ing action  of 
this  muscle  in- 
creasing and 
that  of  the  in- 
ferior oblique 
diminishing  as 
the  eye  is  Jib- 
ducted.  Eye 
carried  out 

mainly   by  ex- 
ternal    rectus, 
'  assisted  by  in- 
ferior oblique, 

especially 
when      abduc- 
tion is  marked. 
Vertical   meri- 
dian      rotated 
out. 
Eye  carried    up 
mainly  by   the  in- 
ferior obliciue,  the 
elevating  action  of 
this     muscle      in- 
creasing and    that 
of  the  superior  rec- 
tus   decreasing  as 
the   eye   is   adduc- 
ted.     Eye  carried 
i»  by  the  internal 
rectus,       assisted, 
especially       when 
adduction  is  mar- 
ked, by  the  super- 
ior rectus, Vertical 
meridian     rotated 


Down 

! Inferior   ]    [In]  "1  Actions 

Rectus             1  equal 
Superior    [Out]  land  op- 

Down. 

[Out]  1  Action 

The  eye  carried 

(Deor- 

[equal     straight  down,  ver- 

sumduc- 

Down. 

[In]     landop-tical   meridian  re- 

tionj 

Oblique.             J  posite. 

Si/ner- 
gists 

J  posite. 

maining    vertical. 
External    and    in- 
ternal     recti      by 
their          counter- 

External   [Out]  )  Actions 

No  action. 

No  action. 

traction    serve    to 

Rectus.              1  equal 

[steady     eye      and 

Internal     [In]    |  andop- 

No  action. 

No  action.          keep  it  in   the  ver- 

Rectus. 1            J  posite. 

tical  line. 

NEW  CLASSIFICATION  OF  MOTOH   ANOMALIES. 


11 


Muscles 
Con- 
cerned. 


Move  Eye 
Laterally. 


Move    Eye 
Vertically. 


Rotate     Upper 
End  of  Verti- 
cal Meridi- 
an of  Cor- 
nea. 


Resultant  Effect 
Upon  Eye. 


Diagon- 
ally 
Down 
and  Out 


Superior. 
Oblique 


External 
Rectus. 


[Inj ;  Action 
slight  and  dim- 
inishing as  eye 
is  abducted. 


Out;  Action 
increasing  as 
eye  is  abduc- 
ted. 


Down;  Ac-  [Out];  Ac- 
tion marked ition  slight  and 
and  increasing  diminishing  as 
as  eye  is  ab-  eye  is  abduc- 
ducted.  ted. 


Down:      Ac-      In;       Action 
tion  slight  and  increasing     as 
diminishing  as  eye    is    abduc- 
eye    is    abduc-  ted. 
ten. 


No  action  No  action. 


The  eye  carried 
doirn  mainly  by 
inferior  rectus, 
the  depressing  ac- 
tion of  this  muscle 
increasing  and 

that  of  the  super- 
ior oblique  fle- 
creasing  as  the 
eye  is  abducted. 
Eye  carried  out 
mainly  by  external 
rectus.  assisted 
especially  in  ex- 
treme abduction, 
by  the  superior 
oblique.  Vertical 
meridian      rotated 


Diagon- 
ally 
Down 
and  In. 


Superior  I  [Out;]  Action 
Oblique,  slight  and  dim- 
inishing es  eye 
is  adducted. 


Rectus  increasing  as 
eye  is  adduc- 
ted. 


Internal    In. 
Rectus. 


Down;      Ac-|     I  In;]    Action 
tion       marked] slight  and  dim- 
and  increasing, inishing  as  eye 
as   eye   is    car-  is  adducted 
ried  inward 


Down;  Action  Out;  Action 
light  and  dim-iincreasing  as 
inishing  as  eyejeye  is  adduc- 
is  adducted.        ted. 


The  eye  carried 
doivii  mainly  by 
the  superior  obli- 
que, the  depress- 
ing action  of  this 
muscle  increasing 
and  that  of  the  in- 
ferior rectus  dim- 
inishing as  the  eye 
is  adducted.  Eye 
carried  in  mainly 
by  the  internal 
rectus,  assisted 
especially  in  ex- 
treme adduction 
by  the  inferior 
rectus;  vertical 
meridian  rotated 
out. 


The  amount  that  the  eye  can  move  in  each  one  of  the  direc- 
tions specified  maybe  determined  experimentally  by  placing  the 
subject  experimented  upon  with  his  eyes  in  the  primary  position 
and  directed  at  an  object  whose  recognition  implies  accurate  fix- 
ation, (e.  g.)  a  fine  double  dot  on  a  card,  and  then  moving  the 
object  in  the  given  direction,  requiring  the  patient  at  the  same 
time  to  follow  it  with  his  eyes,  but  not  with  his  head.  The 
moment  when  he  ceases  to  follow  it  will  be  evidenced  objec- 
tively by  the  perceptible  wavering  of  the  eye,  which  hitherto 
had  steadily  followed  the  object,  and  subjectively  by  the  fact 
that  the  object  itself  becomes  confused  and  no  longer  recog- 
nizable. Then  the  arc  through  which  the  eye  has  rotated  in 
passing  from  the  primary  to  the  terminal  position  may  be 
measured  either  roughly  with  the  eye,  or  accurately  by  some 
form  of  perimeter.* 


*This  may  also  be  accomplished  by  Stevens'  tropometer  or  some 
similar  instrument  which  measures  the  rotation  of  the  eye  by  meas- 
uring the  arc  traversed  by  the  corneal  reflex. 


12 


XKW  CLASSIFICATION  OK  MOTOR  ANOMALIES. 


By  ascertaining  the  limits  of  movement  in  all  directions,  we  de- 
fine the  boundaries  of  the  field  of  fixation  \.  e.,  of  the  entire  space 
through  which  the  visual  line  can  be  carried  without  moving  the 
head. 

The  measurement  of  the  field  of  fixation  in  any  given  case  re- 
quires that  the  patient  under  examination  shall,  in  each  excur- 
sion that  he  makes  with  his  eyes,  put  forth  the  maximum  efifort 
of  which  he  is  capable.  This  he  will  frequently  fail  to  do,  thereby 
making  the  field  appear  incomplete.  It  is  only  by  making  sev- 
eral examinations  and  taking  the  maximum  of  all  the  measure- 
ments, that  we  arrive  at  a  perfectly  reliable  result,  i.  e.,  one  which 
shows  the  full  extent  of  excursion  of  which  the  eye  is  capable. 
The  discrepancies  thus  obtained  in  repeated  examinations  are 
well  shown  in  cases  1,  5,  and  6,  of  the  following  table,  which  is 
constructed  from  observations  of  my  own,  made  upon  normal 
eyes  with  the  perimeter,  and  using  the  fine  double  dot  as  a  test- 
object. 


RIGHT  RYES* 

Case. 

rp 

Up  &  Out 

Up  &  In 

Out 

In 

Down 

Down  &  Out 

Down  &  In 

1  1st  exam. 

40 

35 

40 

35 

40 

70 

33 

J5 

..  2d  exam. 

38 

45 

40 

48 

48 

42 

55 

50 

2 

40 

50 

40 

45 

60 

60 

3 

50 

45 

55 

55 

45 

60 

65 

55 

4        Right  eye  not 

examined. 

5  1st  exam. 

40 

4S 

(50) 

60 

(50) 

62 

65 

(50) 

"  2d  exam. 

40 

4S 

(55) 

50 

(55) 

(62) 

50 

(60) 

"3rd  exam. 

(30) 

42 

(42) 

50 

(45) 

60 

65 

(60) 

6  1st  exam. 

32 

45 

32 

52 

52 

65 

50 

"  2d  exam. 

38 

50 

7 

32 

35 

35 

55 

52 

72 

65 

(62) 

8 

44 

55 

55 

60 

60 

62 

70 

(65) 

9 

50 

50 

60 

52 

(60) 

80 

(70) 

60 

10 

40 

40 

42 

50 

42 

45 

50 

40 

11  1st  exam. 

47 

50 

50 

40 

63 

63 

67 

55 

12         Right  eye  not  examined 

I. 

13 

45 

55 

(55) 

50 

60 

55 

52 

(53) 

14  1st  exam. 

52 

60 

55 

52 

50 

62 

60 

55 

..  2d  exam. 

40 

50 

(45) 

65 

(50) 

65 

SO 

(50) 

15 

(50) 

45 

52 

48 

56 

62 

58 

(60) 

16  1st  exam. 

52 

50 

55 

48 

56 

60 

60 

(50) 

17  1st  exam. 

40 

38 

50 

40 

(45) 

68 

(65) 

(50) 

..  2d  exam. 

47 

52 

52 

48 

(4S) 

60 

(40) 

60 

18 

60 

70 

62 

75 

60 

65 

73 

60 

•Figures  enclo.sed  in  parentheses  mean  that  at  this  point  the  test  object  disappear- 
ed from  view  behind  some  projecting  part  of  tlic  face,  but  at  tlic  time  of  disappear- 
ance was  still  within  the  field  of  fixation. 


NEW  CLASSIFICATION  OF  MOTOR  ANOMALIES. 


13 


LEFT  EYES. 

Case 

rp   I 

•p  &  Out 

Up&  I 

n     Out 

In 

Down 

Down  &  Out 

Down  & 

1    1st  exam. 

.^^l 

40 

45 

35 

45 

70 

60 

50 

..  2d  exam. 

42 

40 

55 

48 

60 

70 

50 

60 

2 

40 

50 

40 

60 

50 

60 

3 

35 

40 

45 

55 

50 

65 

75 

4 

40 

38 

46 

48 

40 

35 

38 

32 

5  1st  exam. 

40 

52 

42 

53 

[48] 

65 

70 

[50] 

..  2d  exam. 

43 

50 

[44] 

52 

48 

[68] 

62 

[48] 

i.  3rd  exam 

42 

50 

40 

48 

[50] 

65 

60 

[50] 

6    Left  eye  : 

not  examined. 

7 

35 

42 

45 

55 

52 

70 

65 

60 

S    Left  eye  not  examined. 

9 

55 

60 

60 

58 

60 

72 

75 

[40] 

10   Left  eye 

not  examined. 

11  1st  exam. 

50 

45 

55 

47 

60 

65 

68 

60 

12 

50 

60 

50 

50 

[60] 

70 

62 

[40] 

13 

[40] 

55 

50 

50 

[50] 

60 

75 

14  1st  exam. 

46 

60 

55 

55 

45 

72 

72 

60 

..  2d  exam. 

15 

48 

50 

50 

56 

55 

65 

60 

[60] 

16  Is  exam. 

48 

55 

52 

55 

52 

60 

55 

•      52 

17  1st  exam. 

40 

42 

[50] 

40 

62 

70 

60 

[52] 

IS  2d  exam. 

44 

50 

50 

48 

[50] 

62 

62 

[40] 

•       58 

71 

71 

72 

62 

72 

76 

68 

The  average  of  the  observations  above  tabulated  gives  ratlier  a 
larger  field  of  fixation  than  has  been  obtained  by  other  experi- 
menters. Thus,  Landolt's  figures,  vs^hile  showing  a  close  agreement 
for  excursions  in  the  upper  field,  are  appreciably  less  for  movements 
downward  (about  50°  in  looking  down,  38°  in  looking  down  and 
out,  and  47°  in  looking  down  and  in).  On  the  other  hand,  the  ex- 
periments of  Schuurmann  and  Uonders  give  the  range  of  downward 
excursion  as  57°,  which  is  somewhat  less  than  those  that  were 
found  by  me,  but  the  upward  excursion  as  only  34°.  This  latter 
figure  certainly  seems  too  small,  in  view  of  the  fact  that  in  but 
one  of  my  cases  was  the  range  as  low  as  this,  and  that  in  nearly 
all  the  others  it  fluctuated  between  40°  and  50°.* 

From  the  range  of  excursion  of  the  eye  in  various  directions, 
we  can  form  a  tolerably  close  estimate  of  the  amotitit  of  xvork 
that  each  muscle  does  in  moving  the  eye. 

For  example,  when  the  eye  is  abducted  30°-35°,  its  movement  up- 
wards is  effected  solely  by  the  superior  rectus,  and,  moreover,  the 
latter  is  then  at  its  maximum  as  an  elevator.  Hence,  to  determine 
the  maximum  elevating  power  of  this  muscle,  we  have  only  to 
measure  the  range  of  excursion  upwards  that  the  eye  can  make 
when  abducted  to  this  extent.  Similarly,  the  range  of  excursion 
downwards,  when  the  eye  is  abducted  30°,  measures  the  maximum 
depressing  power  of  the  inferior  rectus.    Making  use  of  the  results 


*Certainly  the  value  of  20°  found  for  the  range  of  upward  excur- 
sion by  Hering  (cited  in  Gi^aefe-Saemisch)  seems  excessively  small. 
It  is  not  unlikely  that  here  there  was  a  pathological  condition 
present,  such  as  an  insufficiency  of  one  or  both  elevators — a  phe- 
nomenon not  infi-equent. 


14  NEW  CLASSIFICATION  OF   MOTOK  ANOMALIES. 

already  talnilated,*  we  fiud  for  the  maxinnim  elevating  power  of  the 
supevinr  rectus  a  value  of  'S0°,  and  for  the  ?h«.'J?h«?»  depressing  poioer  of 
the  inferior  rectus,  a  nit-an  value  of  3r)'^-40'^. 

The  maximum  elevating  power  of  the  inferior  oblique  and  the 
maximum  depressing  power  of  the  superior  oblique,  are  not  so 
readily  determined,  as  the  eye  can  hardly  be  so  far  abducted  as  to 
enable  these  muscles  to  work  to  the  greatest  advantage,  and  at 
The  same  time  do  away  altogether  with  the  vertical  action  of  the 
superior  and  inferior  recti.  It  would  appear,  however,  that  the 
maxinuim  vertical  effect  exerted  by  the  oblinues,  does  not  differ  materially 
from  that  exerted  by  the  straight  muscles;  only  the  effect  of  the  latter  in 
the  positions  ordinarily  assumed  by  the  eye  is  rather  more  pronounced. 

The  maximum  rotating  effect  of  the  superior  rectus  upon  the  ver- 
tical meridian  (torsion-effect,  swivel-movement)  will  be  ascertained 
by  determining  the  amount  of  deflection  of  the  vertical  meridian 
Avheu  the  eye  is  directed  far  up  and  in.  In  this  situation  the  ver- 
tical meridian  is  not  acted  upon  by  the  other  muscles  capable  of 


Fig.   1. 

rotating  it,  so  that  the  total  rotation  it  undergoes  must  l)e  ascril)ed 
to  the  action  of  the  superior  rectus.  So,  too,  the  rotating  power  of 
the  inferior  oblique,  the  supei-ior  oblique,  and  the  inferior  rectus 
is  measured  by  the  amount  of  tilting  of  the  vertical  meridian  when 
the  eye  is  directed  up  and  out,  down  and  out,  and  down  and  in. 
respectively. 

The  adducting  effect  of  the  superior  and  inferior  recti  and  the 
abducting  effect  of  the  obliques  are  not  determinable  directly  in 
the  normal  eye,  since  these  actions  ;ilw;iys  occur  as  reinforcements 
of  the  adducting  and  abducting  actions  of  tlie  interual  and  external 
recti. 

•■This  can  be  accomplished  by  a  simple  calculation,  based  upon  the 
principles  of  spluM-ical  trigonometry.  'J'luis  if  AB  represents  the 
patli  of  tlie  visual  line  in  passing  from  the  primary  position  obhipiely 
up  and  out,  BC  (or  a)  will  l)e  tlie  elevation  and  AC  (or  b)  tlie  outward 
excursion  or  aliduction  of  the  eye.  Then  Sin.  a  ::=  Sin.  A.  Sin.  c  and 
Sin.  b  =  cot  A.  tan.  a.  Here  c  =  the  range  of  excursion  up  and  out  as 
given  by  our  table  {—  about  45'^),  a  =  ;{0,  and  b  =  3G^. 


XKW    CLASSIFICATION  OF   MOTOK  AXOMAI-IES.  15 

For  the  same  reason,  the  total  adduction  or  abduction  that  the 
eye  is  capal)le  of  is  not  a  precise  measure  of  the  maximum  poicer 
of  the  erternal  and  internal  recti,  since  the  hitter  are  to  a  certain 
extent,  assisted  in  their  action  by  the  vertical  muscles,  and  partic- 
ularly so  when  the  eye  is  already  carried  pretty  far  out  or  in.  It 
is  probable,  however,  from  observations  in'cases  of  paralysis,  that 
the  lateral  action  of  the  vertical  muscles  does  not  amount  to  more 
tliau  4"  or  5°  at  most,  so  that  the  abducting  poirer  of  the  e.'-ternns  may  be 
stated  as  40*-"-45o,  and  the  adducting  power  of  theinternus  as  about  50". 

Passing  now  to  the  third  group  of  fttnctions  under  considera- 
tion, namely  the  character  and  relations  of  the  movements  p  er- 
formed  by  the  two  eyes  when  working  together  we  arc  struck  by 
the  fact  that,  with  unimportant  exceptions,'''  these  movements  are 
limited  to  those  subserving  binocular  fixation. 

Thus,  in  order  to  produce  the  binocular  fixation  of  distant  ob- 
jects, the  visual  lines  must  be  parallel.  In  harmony  with  this 
fact,  we  find  that  there  is  a  whole  series  of  movements — associ- 
ated parallel  inovements — in  which  the  visual  line  of  one  eye  is 
kept  strictly  parallel  with  that  of  the  other;  and,  moreover,  the 
vertical  meridians  of  the  two  cornae  also  remain  parallel,  no  mat 
ter  how  the  eye  is  directed. 

A  second  class  of  movements — iiiovcmeiits  of  convergence — 
adapt  the  eyes  for  the  binocular  fixation  of  near  objects. 

A  third  sort  of  movement  is  that  of  divergence  in  the  horizon- 
tal plane,  causing  the  eyes  to  pass  from  the  consideration  of  a  near 
object  to  that  of  one  more  i emote.  In  doing  this,  this  movement, 
like  the  preceding,  svtbserves  binocular  fixation;  but  it  may 
to  a  certain  limited  extent,  also  antagonize  the  latter  by  carr}-ing 
the  eyes  still  further,  i.  e.,  from  a  position  of  parallelism  to  one  of 
actual  divergence. 

Another  kind  of  movement,  of  very  limited  extent,  is  that  of 
divergence  in  a  vertical  plane^  produced  by  the  elevation  of 
one  visual  line  and  the  depression  of  the  other.  This  move- 
ment, called  sursumvergence  (or  deorsumvergence)  is  denoted 
as  right  or  left,  according  as  the  right  or  left  visual  line  is 
higher  (or  lower). 


*The  exceptions  are  very  clearly  described  by  Helmholtz  (Phys. 
Optik,  2d  Ed.,  pp.  631,  et  seq.)  He  seems  to  me,  however,  to  have 
laid  too  much  stress  upon  the  ability  of  the  eye  to  make  exceptional 
movements  of  this  sort;  the  fact  being  that  such  movements  ar.- 
extremely  limited  and,  beyond  a  certain  point,  cannot  be  increased 
by  practice.  It  seems,  therefore,  that  in  spite  of  his  statement 
to  the  contrary,  there  is  some  anatomical  basis  for  the  inability  of 
the  eye  to  make  unaccustomed  movements  and  tliat  it  is  not  simply 
a  question  of  training. 


16  NEW  CLASSIFICATION  OF  MOTOR  ANOMALIES. 

A  fifth  class  of  iiioveinents  comprise  those  in  which  the  vertical 
niv)-idia7is  of  the  two  cornccc  are  so  rotated  as  to  be  no  longer 
parallel.  Such  a  rotation  occurs  normally  in  positions  of  marked 
convergence,  the  vertical  meridians  then  diverging  at  their  up- 
per extremities,  and  the  amount  of  divergence  increasing  as  the 
eyes  are  elevated  (Meissner,  Le  Conte).  But,  apart  from  this 
physiological  torsion-movement,  a  divergent  or  convergent  ro- 
tation of  the  vertical  meridians  may  be  produced  in  the  normal 
eye  and  demonstrated  by  suitable  apparatus  (Helmholtz). 

The  Associated  Parallel  Movements  of  the  two  eves  with  the 
muscles  concerned  in  their  production  are  shown  in  the  follow- 
ing tables: 


NEW  CLASSIFICATION  OF  MOTOR  ANOMALIES. 


17 


Both    I 
Eyes 
Movetoi  R.  Eye 


Muscles  con- 
cerned 


Move  eyes 
laterally* 


Move  eyes 
vertically* 


meridians  '     " 

ofcorneae. 


1 

Right  j 

External       Internal 

To  R. 

! 

No  action 

No  action 

R  eye  carried 

Rectus            Rectus 

toRby  the  ex- 

(Dex- 

ternal  rectus 

1 

assisted  by  the 

sion.) 

Synergists 

[ToL    a&. 

obliques: 

L  eye   carried 
to  R  by  intern- 

Superior     Inferior  1 

To  R,  ac- 

Down actions 

al  rectus  assist- 

Oblique        Rectus      ' 

tion    in- 

1 equal 

O  0 

ed  by  the  supe- 

creasing 

andop- 

rior  and  infer- 

Inferior     Superior 

the  more 

i  posite 

S3 

ior  recti.    The 

Oblique          Rectus  J 

eyes  are 

[Up 

[•ToR    ^-c 

other   muscles 

carried 

J  C  £. 

act  to  steady 

1 

UoR 

the  eyes  and 
keep  them    in 

Opponents. 

the   horizontal 
plane.  Vertical 

Superior      Inferior! 

■  [To  L]  ac- 

[UpJ 

Actions 

[ToLlgS 

meridiansboth 

Rectus         Oblique     i 

tion  sli't 

equal 

S"? 

remain  verti- 

I 

&  dimin- 

and op- 

'■2 '^ 

cal. 

Inferior      Superior 

ishing  as 

posite 

Rectus         Oblique  J 

1  eyes  are 
1  carried 

[Down 

0  n 

[Tor    ^-I 

i 

I  to  R. 

n  p 

Left 

Internal      External 

ToL- 

No  action.       No  action 

R.  eye  carried 

Rectus          Rectus     ' 

to  L.  by  the  in- 

(Sinis- 

ternal  rectus, 

1  assisted  by  the 

sion.) 

Synergists.            \ 

ToL 
action 

~1     ac- 

]  g  ^  1    superior  and 
c.-.'  inferior  recti: 

Superior      Inferior 

increas 

[ U p  1          tions   [ To  L  1  o  §  '  L.   eye  carried 

Rectus         Oblique 

es  the 
more 

.equal              ^§  »  :  to  R.  by  theex- 

and                   go     ternal  rectus, 

[Down      oppo-;[ToR     ^-c   assi.sted  by  the 

J    site.  !            h^'  obliques.     The 

1                       t  other  muscles 

Inferior       Superior 
Rectus         Oblique 

eyes 
are  car- 
ried to 

T.. 

act  to  steady 

1   the  eyes  and 

Opponents. 

[To   R] 

"1     ac- 

keep  them  in 
1  »  »  1  the   horizontal 

Superior      Inferior 
Oblique        Rectus 

B^ 

[Down      tionsi[ToL     §.»  plane    Vertical 

equall                o  o     meridians  re- 

f    and  1               §  S  i  maiii  vertical 

Inferior      Superior 

|Up]     oppo-[ToR     o^ 

Oblique        Rectus 

J    site.               J  || 

1 

[ToL]|§ 

i                             ;[ToLl 

S^L  ,u 

Up 

1     Superior     Inferior 

Up 

acr.lBoth  eyes   car- 

Rectus     Oblique 

o  g  I  ried  vertically 

[Sur- 

1 

t)  S    up  by  combiu- 

suni- 

1.1 

■grt  ied  action  of  su- 

ver- 

ii.c     perior  rectus 

sion.] 

1     Inferior     Superior 
Oblique     Rectus 

[ToR]i''£ 

Up 

[ToR 

g^£,l     and  inferior 
oblique.  Exter- 
nal and  inter- 

Si/nergists. 

>» 

i  ual  recti  act  to 
steady  eye  and 

External    Internal 
Rectus       Rectus 

[ToR] 

No  action 

No  action   keep  it  in  verti- 
cal plane.    Ver- 
tical meridians 

1     Internal    External 

" 

remain  verti- 

Rectus        Rectus 

[To  L]  ^•g 

... 

*Portions  enclosed 
ized. 


brackets  indicate  movements  which  are  completely  neutral 


18 


XEW  CLASSIFICATION   OF   MOTOR   ANOMALIES. 


Both     Muscles    coucerued 

Eyes 

Move      R  Eye         •  L  Eye 


and 
to  R. 


and  to 
L. 


Move  eyes 


t-ertically 


Rotate  up- 
per ends  of 

vertical 
meridians 
of  corneae 


Resultant 
effects    up- 
on eyes 


Superior     Inferior 
Rectus        Oblique 


Inferior     Superior 
Obliciuc      Rectus 


Syiierglsti. 


External    Internal 
Rectus       Rectus 


[To  L.]         Up.  Action 
Action  marked  and 

slight  and     increasing  as 
decreasing    eyes  are  ear- 
as  eyes  are  ried  to  R. 
carried  to  R 
I 
To  R.  Up.  Action 

Actions      slight   and  de 
marked  &     creasing  as 
increasing  |  eyes  are  ear- 
as  eyes  are iried  to  R. 
carried  to  R 


[To  I J   Ac- 
tion slight 

and   de- 
creasing as 
eyes  are 
carried  to R 

To  R. 

Action 
marked  & 
increasing 
as  eyes  are 
carried  to  R 
No  action. 


R.  eye  carried 
up  by  superior 
rectus;  L. by  in- 
ferior oblique. 
R.  eye  carried 
to  R.  by  exter- 
nal rectus  as- 
sisted (espec- 
iallyin  extreme 
abduction )  by 
inferior  obli- 
que: L.  eye  car- 
ried to  R  by  in- 
ternal rectus 
assisted  by  su- 
perior rectus. 
Both  vertical 
meridians  tilt- 
ed to  R. 


Inferior    Superior 
Oblique      Rectus 


Superior    Inferior 
Rectus     Oblique 


Sinierffiutt^ 


[ToR]  Ac-    Up.  Action 
jtion    slight  marked  and  in- 
&  decreas-  creasing  as 
ling  as  eyes  eyes  are  car- 
are  carried  ried  to  R 
to  L. 
I  I 

To  L.  Up.     Action 

I     Action      I  slight  and  de- 
marked    &  creasing  as 
increasing  eyes  are  ear- 
as  eyes  are  |  ried  to  L. 
carried  toL 


[To  Rl  Ac- 
tion slight 
&  decreas- 
ing as  eyes 
are  carried 
to  I,.  ! 


To  L  Ac- 
tion mark- 
ed and  in- 
creasing as 
eyes  are 
carried  to 


Internal     External  To  L. 

Rectus        Rectus 


R.  eye  carried 
up  mainly  by 
inferior  ob- 
lique, I,  eye  by 
superior  rec- 
tus:  R  eye  car- 
ried to  L  by  in- 
ternal rectus 
assisted  by 
superior  rec- 
tus. L  eye  car- 
ried to  L  by  ex- 
ternal     rectus 
assisted  by  in- 
ferior oblique. 
Vertical  meri- 
dians both  ro- 
tated to  L 


Down 

(Deor- 
sum 
ver- 
sion) 


Inferior     Superior 
Rectus      Oblique 


Superior     Inferior 
Oblique      Rectus 


Si/nerfflsts. 


External     Internal 
Rectus       Rectus 


Internal       External 
Rectus       Rectus 


[ToR 


[ToRl  9?", 


[ToLhS 


[Tol 


[To  R  I  R?^   Both  eyes  car- 
o  a!  ried  vertically 
I  2  S  !  down  by  com- 
bined action  of 
inferior  rectus 
and  superior 
oblique.     Ex- 
ternal and 
internal  recti 
act  to  steady 
I  eyes  and  keep 
hen 

■  ertical  plane. 
Vertical  mer- 
idians remain 
vertical. 


NEW  CLASSIFICATION  OF  MOTOR   ANOMALIES. 


19 


Both 
Elyes 
Move 


Muscles    concerned 
R  Eye  L  Eye 


Move   eycf 
laterally 


Down 
and  to 
R. 


Inferior       Superior 
Rectus  Oblique 


Superior 
Oblique 


[To  L.]  Ac 
tiou  slight 
&  decreas 


Inferior     To  R.  Ac- 
Rectus    tions 

marked    & 
increasing 


Move  eyes 
vertically 


Rotate  up- 
per ends  of 

vertical 
meridians 
of  cornese 


Si/nergists. 


External       Internal 
Rectus  Rectus 


Down.     Action 
marked  and  in- 
creasing as 
eyes  are  car- 
ried to  R 


Down.  Actions 
slight  and   de- 
creasing as 
eyes  are  ear- 


as  eyes  are   ried  to  R. 
carried  to 


[To  R.] 
Action 
slight  and 
decreasing 
as  eyes  are 
turned  to 
R. 

ToL. 
Action 
marked 
and  in- 
creasing as 
eyes  are 
carried  to 
R. 

No  action. 


Resultant 
effects   up- 
on eyes 


R.  eye  carried 
down  mainly 
by  inferior 
rectus,  R.  eye 
by  superior  ob- 
lique, R.  eye 
carried  to  R  by 
external  rec- 
tus assisted  by 
superior  ob- 
lique, L-  by 
internal  rectus 
assisted  by 
inferior  rectus. 
Both  vertical 
meridians  ro- 
tated to  L. 


Down 
and    to 


Superior     Inferior 
Oblique     Rectus 


Inferior    Superior 
Rectus       Oblique 


Synergists. 


Internal    External 
Rectus      Rectus 


[To  R.]  Ac- 
tion slight 
and  de- 
1  creasing  as 
jeyes  are 
carried  to 
L. 


;To  L.    a 
Jtion 
marked 
and  in- 


Down.     Ac- 
tion malted 
and  increasing 
as  eyes  are 
carried  to  L. 


[ToL.]  Ac- 
tion slight 
and  de- 
creasing as 
eyes  are 
carried  to 
L. 


creasing  as  ried  to  L. 
eyes  are       i 
carried  to 

,L.  I 


Down.     Action  To  R 
slight  and  de 
creasing  as 
eyes  are 


To  L. 


No  action. 


Ac- 


tion 
marked 
and  in- 
creasing as 
eyes  are 
carried  to 
L. 

No  action. 


R.  eye  carried 
down  mainly 
by  superior 
oblique,  L.  by 
inferior  rectus. 
R.  eye  carried 
toL.bj' internal 
rectus  assisted 
by  inferior 
rectus;  L. 
eye  carried 
to  L.  by  exter- 
nal rectus  as- 
sisted b}'  supe- 
rior oblique. 
Both  vertical 
meridians  ro- 
tated to   R. 


An  inspection  of  the  tables  just  given  will  show  that  in  all 
parallel  movements  of  the  eyes  each  muscle  acting  upon  the 
right  eye  is  associated  with  a  muscle  which  acts  upon  the  left 
eye  in  a  precisely  similar  manner,  and  to  a  precisely  equal  extent. 
Such  a  pair  of  muscles,  one  in  each  eye,  are  termed  associated 
antagonists  (A  Graefe). 

Thus  the  superior  rectus  of  one  eye  and  the  inferior  oblique  of  the 
other  are  associated  antag-onists.  since  in  all  positions  that  the  two 
eyes  may  assume,  these  muscles  move  their  respective  eyes  to  the 
same  extent  and  in  the  same  direction,  so  that  if  they  acted  alone 
they  would  always  keep  both  visual  lines  and  both  vertical  meri- 
dians parallel.  The  associated  antagonists  and  their  action  may  be 
summarized  as  follows: 


20 


NKW  CLASSIFICATION   OF   MOTOR  ANOMALIES. 


ASSOCIATED    ANTAGONISTS. 


Muscle. 
R.  eye. 

Moves  eye 

laterally 

to 

Moves  eye 
1  Vertically 

i 

Vertical 
action  in- 
creasing & 
Rotates  up-  latent  ac- 
per  end  of  tiondimin- 
vertical       ishing  as 
meridian      eyes  are 
cornea     | turned  to 

ASSOCIATED 

ANTAGONIST. 

L  eye 

External  Rectus 

R 

No  action 

1 
No  action  ! 

Internal    Rectus 

Internal  Rectus 

L 

No  action 

No  action 

External  Rectus 

Superior  Rectus 

L 

;      Up 

h                    R 

Inferior  Oblique 

Inferior    Rectus 

L 

Down 

R                       R 

Superior  Oblique 

Superior  Oblique 

R 

Down 

L                     I. 

Inferior  Rectus 

Inferior  Oblique 

R 

1     - 

R                     L 

Superior  Rectus 

The  determination  of  the  ra??/fe  of  excursiojt  in  associated 
■parallel  movements  comprises  the  solution  of  two  distinct  prob- 
lems, namely,  the  determination  of  the  field  of  binocular  single 
vision  and  the  determination  of  the  field  of  binocular  fixation. 
We  delimit  the  Jield  of  binocular  fixation  by  ascertaining  for 
each  direction  of  the  gaze  the  point  at  which  either  one  of  the 
eyes  fails  to  follow  an  object  moving  before  the  two.  This 
can  be  done  very  conveniently  with  the  double  dot  used  for 
testing  the  monocular  field  of  fixation,  since  the  moment  when 
either  eye  fails  to  follow  the  dots  or  when  either  eye  fails  to 
keep  up  with  the  other  in  following  them,  is  rendered  evident 
by  a  blurring  of  the  image  causing  the  two  dots  to  run  into  one. 

Heriug:,  who  used  a  different  method  (with  after-images),  found 
the  binocular  field  to  be  of  quite  small  extent,  being  considerably 
smaller  than  the  portion  common  to  the  tAvo  monocular  lields. 

It  seems  likely,  however,  that  his  tests  in  this  case,  as  in  the  ease 
of  the  monocular  Held,  were  made  upon  a  not  altogether  normal  sub- 
ject. My  own  researches,  altliough  few,  to  be  sure,  were  made  upon 
quite  normal  individuals.     They  gave  the  following  results:* 

MOVEMENTS  OF  BOTH  EYP^S. 

Down  and    Down  and 
risht.  left. 


TT„     Up  and    Up  and     tj:„v,. 
Up-     right.         left.        K'^^^- 


Left.      Down. 


Case  I.... 

..  38 

fi'i 

4.5 

58 

52 

Case  11... 

..  50 

r)2 

53 

06 

n'.t 

The  delimitation  of  the  field  of  binocular  single  vision  is  ef- 
fected by  noting  in  any  particular  direction  Of  the  gaze  the  point 
at  which  one  eye  can  no  longer  keep  pace  with  the  other,  as 
evidenced  by  the  development  of  an  insuperable  diplopia. 

The  field  defined  by  joining  all  such  points  is  not  necessarily  coin- 
cident with  the  field  of  binocular  fixation,  since  it  is  quite  conceiv- 
able that  the  two  eyes  folloAving  a  moving  object  might  fail  to  fix 


lOxaminatidu  made  for  near  ]><)ints. 


NEW  CLASSIFICATION  OF  MOTOR  ANOMALIES. 


21 


it,  but  might  yet  both  lag  behind  to  au  equal  extent,  so  that  the 
two  images,  although  not  formed  upon  the  macula;,  would  still  be 
formed  upon  corresponding  points.  In  this  case,  binocular  single 
vision  would  still  be  present,  although  binocular  fixation  would  no 
longer  exist. 

A  point  upon  which  some  stress  has  been  laid  is  that  this  method 
of  delimiting  the  held  of  fixation  gives  uncertain  results,  since,  as 
is  alleged,  many  people  fail  to  recognize  diplopia  in  eccentric  posi- 
tions of  the  gaze.  It  is  claimed,  in  other  words,  that  the  normal 
field  of  binocular  single  vision  is  quite  small,  and  that  diplopia 
occurs  normally  in  looking  far  up,  far  to  the  right,  etc.,  but  that 
its  existence  is  not  suspected,  because  the  subject  under  examination 
either  fails  to  notice  or  actually  suppresses  one  image.  My  own 
experiments,  however,  lead  me  to  negative  this  idea  completely.  If 
we  employ  a  candle  for  our  test-object,  and  place  a  red  glass  before 
oue  eye  of  the  individual  examined,  the  presence  of  binocular  single  vision 
will  be  shown  by  the  fact  that  the  candle-flame  appears  pinkish  or,  more 
commonly  yellow  with  a  reddish  border.  Manifest  diplopia  will  be  shown 
by  the  presence  of  two  flames,  one  red  and  the  other  yellow,  and  dip- 
lopia with  the  snppression  of  either  image  by  the  presence  of  one  flame, 
either  pure  red  or  pure  yellow.  The  differences  presented  are  marked 
and  readily  appreciated  by  an  intelligent  patient  when  once  they  have 
been  pointed  out  to  him. 

Testing  in  this  way  a  large  number  of  people  with  apparently 
normal  eyes,  I  have  uniformly  found  that  the  field  of  binocular 
single  vision  extends  not  less  than  40°  in  atzy  given  direction 
and  usually  extends  up  to  50°  or  more.  Indeed,  most  persons 
still  get  true  binocular  single  vision,  even  when  the  eyes  are 
carried  to  the  extreme  limit  of  their  excursion,  the  field  of  bin- 
ocular single  vision  being  larger  than  either  monocular  field 
of  fixation  taken  separately.  This  is  but  another  instance  of 
the  law  that  the  movements  of  the  eyes,  however  extensive  or 
however  limited  in  themselves,  are  always  under  normal  con- 
ditions modified  in  such  a  way  as  to  best  subserve  binocular 
fixation  and  binocular  single  vision.  Thus,  as  the  experiments 
just  adduced  seem  to  show,  it  appears  that,  no  matter  what  the 
maximum  range  of  excursion  of  each  eye  separately  is,  the  ex- 
cursion of  both  together,  effected  by  the  co-ordinating  action 
of  the  association-centres,  is  such  that  one  eye  keeps  pace  with 
the  other,  going  neither  faster  nor  slower,  and  that  each  stops 
moving  when  the  other  does.  Hence,  however  far  the  object 
looked  at  may  be  carried  in  any  given  direction,  no  diplopia 
occurs,  or,  if  it  does,  it  is  transient  and  superable.* 


*These  statements  presuppose  (1)  that  the  visual  lines  are  not 
far  from  parallel,  i.  e.,  the  test-object  should  not  be  less  than  :: 
feet  from  the  eyes:  and  (2)  the  person  examined  should  endeavor  all 
the  time  to  follow  the  o^bject.  i.  e.,  must  not  look  beyond  it.  In  the 
latter  case,  of  course,  the  test-object  will  seem  to  him  double.  Such 
diplopia  is.  however,  usually  at  once  superable  by  voluntary  effort. 


22  NEW  CLASSIFICATION'  OF   MOTOK   ANOMALIES, 

Each  of  the  main  associated  parallel  movements  turning 
(dextroversion,  or  the  turning  of  both  eyes  to  the  right, 
sinistroversion,  or  the  turning  of  both  eyes  to  the  left,  sur- 
sumversion,  or  parallel  movement  up,  and  deorsumversion,  or 
parallel  movement  down)  is  apparently  fresided  over  by  a  dis- 
tinct nucleus  (association  centre).  The  precise  location  of  these 
centres  has  not  been  satisfactorily  determined,  but  the  evidence  of 
their  existence  from  pathology  is  very  strong,  lesions  in  which 
dextroversion  and  sinistroversion  alone  are  afifected  being  not  in- 
frequent, and  isolated  involvement  of  sursumversion  also  hav- 
ing been  recorded.     These  facts  will  be  referred  to  later  on. 

Movements  of  convergence  may  be  regarded  as  associated 
parallel  movements  to  which  a  simultaneous  contraction  of 
both  interni  has  been  superadded.  Thus  in  looking  at  a  near 
object  situated  up  and  to  the  right  there  is  a  movement  of  sur- 
sumversion and  dextroversion  combined  with  a  contraction  of 
both  interni,  which  neutralizes  in  part  the  right-hand  move- 
ment of  the  right  eye,  and  reinforces  the  right-hand  movement 
of  the  left  eye. 

This  double  contraction  of  tlie  interni  is  presided  over  by  a 
special  centre  (convergence  centre)^  distinct  from  the  association 
centres  for  parallel  movements. 

Convergence,  when  marked,  modifies  somewhat  the  effect  of  the 
other  muscles  that  are  acting  with  tlie  interni.  Thus  when  the  gaze 
is  directed  at  a  near  object  in  the  median  line,  the  superior  rectus 
of  one  eye  and  tlie  inferior  oblique  of  the  other  no  longer  act  as 
associated  antagonists,  the  fonner  serving  mainly  to  adduct,  and 
the  latter  to  elevate  the  eye.  In  this  case,  in  fact,  the  superior  and 
inferior  obliques  in  each  eye  neutralize  each  other  completely,  and 
the  two  superior  and  two  inferior  recti  act  as  synergists  to  the  two 
interni,  all  adducting  the  eye.  Again,  when  the  gaze  is  directed 
at  a.  very  near  object,  situated  upward  and  to  the  right,  the  right 
superior  rectus,  since  the  right  eye  is  not  pointed  as  far  to  tlie 
right  as  the  left  one  is,  will  not  be  working  as  an  elevator  at  quite 
the  same  mechanical  advantage  as  does  the  left  inferior  oblique. 
Theoretically,  therefore,  the  right  eye  will  lag  somewhat  below  thf 
left.  Practically,  I  have  not  observed  this  to  occur,  although  it 
does  seem  to  me  that  the  field  of  binocular  single  vision  is  smaller 
for  convergent  than  for  parallel  movements. 

The  tnaximtini  power  of  convergence  is  obviously  represented 
either  by  the  angle  formed  by  the  two  visual  lines  when  both 
eyes  are  turned  in  to  their  utmost  extent,  or  by  the  distance  from 
the  eyes  of  the  nearest  possible  point  upon  which  they  can  be 
converged.  This  point  is  called  the  fusion  near-point,  or.  better 
the  near-point  of  convergence  (Pc.)  Bonders  in  a  boy  of  lo 
found  the  maxinuim  angle  of  convergence   to   be   70*^,   which, 


NEW  CLASSIFICATION  OK   MOTOlt  ANOMALIES.  23 

with  an  interocular  distar.ce  of  00  mm.,  would  signify  a  near- 
point  of  convergence  situated  52  mm.  from  the  centre  of  rotation 
of. either  eye  and  42  mm.  in  front  of  the  hne  joining  the  centres 
of  both  eyes ,  or  about  1^"  from  the  cornea  and  ^"  in  front  of 
the  bridge  of  the  nose.  Some  can  converge  to  even  a  greater 
extent.  Prof.  Le  Conte,  for  example,  who  had  acquired  ex- 
traordinary facility  in  the  use  of  his  eyes,  had  a  convergence- 
angle  of  nearly  90=*.  Schuurmann,  on  the  contrary,  found  a 
maximum  convergence-angle  of  only  43°,  which  would  corre- 
spond to  a  convergence  near-point  situated  about  25"  from  the 
corneie  and  22"  in  front  of  the  bridge  of  the  nose  ;  and  v.  Graefe 
gives  to  the  convergence-angle  a  value  of  00°  corresponding  to 
a  distance  of  2"  from  the  eye,  and  1^-''  from  the  bridge  of  the 
nose.  My  own  experience  leads  me  to  regard  Schuurmann's 
figures  as  expressing  most  nearly  the  results  found  in  the  general 
average  of  cases,  the  convergence  near-point  in  the  majority 
of  normal  persons  that  I  have  examined  being  situated  at  about 
1"  in  front  of  the  nose.  A  distance  of  \\"-\L"  may,  in  fact,  be 
regarded  as  the  normal  for  adults.  Children  often  have  a  greater 
power  of  convergence,  and  in  them  the  distance  may  not  ex- 
ceed V .  A  distance  of  less  than  1"  denotes  excessive,  and  one 
of  over  2^''  deficient  convergence-power. 

Another  method  of  determining  the  power  of  convergence  is 
by  ascertaming  the-  sfreno-//i  of  prism,  which  can  be  overcome 
by  the  eyes  when  placed  before  the  latter  with  its  base  out  or 
towards  the  temple. 

This  method  is  analogous  to  that  employed  by  Donders  for  de- 
termining the  positive  portion  of  the  range  of  accommodation.  TIi3 
strength  of  prism  overcome,  in  fact,  represents  the  amount  of 
residual  convergence*  that  the  subject  under  examination  can  ex- 
ercise when  his  eyes  are  adjusted  for  the  distance  of  the  test-ob- 
ject employed,  just  as  the  strength  of  the  concave  glass  that  he 
can  overcome  represents  tlie  amount  of  his  residual  accommodaiion 
under  the  same  conditions.  The  amount  of  this  residual  conver- 
gence naturally  varies  with  the  distance  of  the  test-object,  decreas- 
ing as  the  latter  is  brought  nearer.  It  also  varies  considerably  for 
the  same  distance  in  different  individuals,  until  the  latter  have  by 
training  learned  to  do  what  at  the  outset  is  quite  difficult  for  them, 
namely,  to  look  at  a  distant  object  and  at  the  same  time  direct 
their  eyes  as  if  it  were  much  nearer  than  it  really  is.  When  this  art 
has  been  learned,  it  will  be  found  that. 

Normal  subjects  will  for  test-objects  at  a,  distance  of  twenty 
feet  overcome  prisms  of  00°-70°  refracting  angle  (equivalent  to 
a  convergence  of  40°-.50°),  so  that  the  maximum  convergence 
produced  in  this  way  equals  that  produced  in  the  natural  fashion, 
i.  e.,  by  looking  at  a  very  near  object. 

♦Often  improperly  called  the  adduction. 


Cor 

responding    amount 
accommodation   for 

Actual  amount  of 

con- 

of 

vcrgence  produced  by 

Accommodation  ex- 

a natural  convei-gence 

overcoHiingtliepi 

risiu. 

erted. 

of  the  same  degree. 

4.3" 

0.25 

1.25 

6.5^ 

0.50 

2.00 

11.00^ 

1.50 

3.25 

15.5'^ 

2.50 

4.50 

19.3° 

5.00 

5.50 

24  XEW  CLASSIFICATION  OF  MOTOR  ANOMALIES. 

Convergence  thus  produced  by  prisms  is  at  first  associated 
with  an  accoiiinwdative  effort  similar  to,  but  less  than  that  ac- 
companying a  natural  convergence  of  the  same  degree.  Thus 
two  cases  that  I  examined  showed  the  following  amount  of  ac- 
commodation : 


Ctiise  1 
Case  2 . 


By  continual  practice,  however,  the  patient  may  learn  to  relax 
the  accommodation  while  maintaining  the  convergence,  and  in  this 
way  prisms  of  20°  or  30°,  base  out,  may  be  overcome  without  the 
accommodation  being  used  at  all.  I  have  met  with  an  extreme  in- 
stance of  this  sort  in  which  the  patient  could,  without  making  any 
accommodative  effort  whatever,  overcome  prisms  representing  a 
convergeuce-angle  of  nearly  40°. 

Divergence,  or  the  simultaneous  lateral  separation  of  the 
visual  lines,  is  a  process  which  ordinarily  subserves  binocular 
fixation,  being  used  when  the  eyes  fix  in  succession  objects  more 
and  more  remote.  The  process  may,  however,  be  performed 
to  excess,  so  that  the  visual  lines  diverge  from  the  object  of  fixa- 
tion, as  when  the  homonymous  diplopia  caused  by  a  prism 
placed  base  in  before  the  eye  is  overcome,  or,  on  the  other  hand, 
an  involuntary  or  voluntary  crossed  diplopia  is  produced  by 
turning  the  eyes  outward. 

Divergence  of  the  sort  last  mentioned,  i.  e.,  that  giving  rise 
to  a  crossed  diplopia,  varies  greatly  in  amount,  and,  although  re- 
garded as  normal  by  those  experimenters  who  have  acquired  a 
peculiar  facility  in  producing  it,  is  probably  to  be  classed  among 
the  abnormalities.  At  all  events,  there  are  not  many  in  whom  the 
phenomenon  is  habitual,  or  who  can  produce  it  at  will,  and  when 
present,  it  is  generally  associated  with  lack  of  muscular  balance, 
and  other  evidences  of  a  pathological  state. 

On  the  other  hand,  a  divergence  produced  in  the  act  of  over- 
coming a  prism  placed,  base  in,  before  the  eyes,  is  an  entirely 
normal  phenomenon  of  very  definite  character.  Its  maximum 
amount  naturally  varies  with  the  distance  of  the  object  of  fixa- 
tion, increasing  as  the  latter  approaches  the  eye.  The  strength, 
in  fact,  of  the  prism,  base  in,  that  the  eyes  can  overcome  when 
regarding  an  object  at  any  given  distance,  represents  the  amount 
by  which  the  eyes,  when  converged  upon  the  object  and  accom- 
morlatod  for  tlic  latter,  can  diverge;  jxist  as  the  strength  of  the 


NEW  CLASSIFICATION  OF   MOTOR  ANOMALIES.  20 

convex  glass  that  can  be  overcome  in  looking  at  the  object  rep- 
resents the  negative  portion  of  the  range  of  accommodation  for 
the  same  distance.  For  distance,  i.  e..  when  the  visual  lines  are 
parallel,  the  divergence*  amounts  quite  regularly  to  from  3°  to 
5°  (=  divergence  produced  in  overcoming  a  prism  of  6°  to  10°) ; 
and  variations  above  or  below  these  limits  must  be  regarded  as 
distinctly  pathological. 

As  to  the  true  nature  ofdivergt^nce,  i.  e.  ;  whether  it  consists  in 
an  active  muscular  contraction  as  in  the  case  of  convergence,  or 
whether  it  is  simply  a  relaxation  of  the  interni,  allowing  the  eyes 
to  return  to  a  position  of  rest,  there  has  been  much  difference  of 
opinion. 

Those  who  adopt  the  hitter  view  assume  that  the  natural  position 
of  the  eyes,  i.  e.,  that  in  which  all  the  muscles  are  fully  relaxed,  is 
one  of  slight  divergence,  parallelism  itself  requiring"  a  certain  tonic 
and  constant  contraction  of  the  interni  for  its  maintenance  (Hansen 
Grut).  Some  liave  even  thought  that  the  position  of  complete  re- 
laxation is  that  in  which  each  visual  axis  coincides  with  the  axis 
of  the  orbit — a  state  of  things  implying  a  divergence  of  25°-30°  (l.e 
Conte).  Those  who  thus  think,  however,  appear  to  be  misled  in 
reg'arding  as  natural  a  condition  which  is  abnormal,  not  to  say  patho- 
logical. Schweigger  lias  argued  strenuously  against  Hansen  Grut's 
theory  and  especially  to  his  application  of  it  as  explaining  the 
nature  of  divergent  squint,  and  Sehueller  also  has  adduced  a  variety 
of  arguments,  which,  however,  are  not  very  convincing,  to  prove 
that  the  function  of  divergence  is  an  active  process.  For  my  own 
part,  I  believe  that  in  the  majority  of  cases  the  poisition  of  perfect 
physiological  rest  is  not  one  of  divergence  and  that,  consequently, 
the  lateral  separation  of  the  visual  lines  must  be  regarded  as,  in 
part  at  least,  an  active  process  due  to  simultaneous  contraction  of 
the  externi.  One  argument  in  favor  of  this  is  that  many  people, 
when  we  test  their  divergence  with  prisms,  experience  a  marked 
sense  of  strain  analogous  to  that  felt  in  overcoming  prisms  by  con- 
verg'ing  the  eyes.  The  latter  is  certainly  an  active  process,  and  the 
former,  therefore,  in  these  cases  at  least,  would  seem  to  be  one  also. 
Patients,  to  be  save,  who  can  diverge  at  will  so  as  to  produce 
crossed  diplopia,  often  assure  us  that  they  do  so  by  "relaxing"  tlie 
eyes;  but  several  o'bservations  have  convinced  me  that  this  relaxa- 
tion is  really  a  muscular  contraction. f 

Perhaps  the  strongest  argument  in  favor  of  the  idea  that  diver- 
gence is  a  passive  and  not  an  active  process  is  that,  in  the  great 
majority  of  cases  at  least,  the  diverging  power,  as  measured  h>i 
the  ability  to  overcome  prisms,  base  in,  can  not  be  increased  at  all 
beyond  the  initial  amotmt,  shown  by  the  subject  experimented  upon 
If.  for  exatnii>le.  in  our  first  ti'ial  of  a  patient,  at  the  maximum  prism. 
base  in,  that  he  can  overcome  is  one  of  8°,  we  s'hall  generally  find 

♦Usually  but  improperly  called  the  abduction. 

fA  similar  instance  in  which  an  undoubted  muscular  contraction 
was  described  by  the  patient  as  a  "relaxation"  was  one  that  I  met 
with,  in  which  an  homonymous  diplopia  of  15°  (prism)  was  produced 
at  will.  Here,  of  course,  a  condition  of  convergence  was  present, 
which  could  only  have  been  brought  about  by  an  active  contraction 
of  the  interni. 


2G  NEW  CLASSIFICATION  OF  MOTOH   ANOMALIES. 

that  we  can  not  get  him  beyoud  this  ixjiut  by  aiiy  amouut  of  sub- 
sequent traiuiuy.  If  divergence  were  a  process  of  active  muscuku- 
contraction  it  would  seem  as  if  it  ouglit  to  be  su8ceptil)le  of  being 
increased  by  exercise. 

But  whatever  the  nature  of  divergence,  whether  active  or  pas- 
sive, it  is  certainly  a  distinct  function  of  the  eyes,  and  probably 
regulated  by  a  distinct  nervous  mechanism.  The  evidence  af- 
f(^rdcd  by  patliology,  at  all  events,  point  very  stronglv  in  this 
direction. 

Separation  of  the  visual  lines  in  a  vertical  plane  (sursumduc- 
tlon,  or,  inore  properly,  sursumvergence)  is  a  movement  which 
all  normal  eyes  can  perform.  It  is,  however,  very  limited  in 
amount,  not  normally  exceeding  1°  or  1|°  {=  the  divergence 
produced  by  a  prism  of  2°  or  3°).  It  is  evidently  an  active  pro- 
cess associated  with  a  sense  of  considerable  strain,  and  appears 
susceptible  of  being  increased  by  exercise,  particularly  in  those 
that  have  a  natural  or  acquired  vertical  deviation  (hyperphoria). 

The  power  of  producing  convergence  or  divergence  of  the 
vertical  meridiaas  of  the  two  eyes,  the  visual  lines  remaining 
parallel,  is  a  subject  about  which  very  little  is  known.  Even  the 
experiments  of  Helmholtz,  which  seem  to  prove  its  existence, 
have  been  called  into  question  by  some,  althotigh  probably  with- 
out sufficient  reason. 

Appendix.  The  analysis  of  the  complicated  problems  involved  in 
the  study  of  the  mnvenients  of  the  eyes  may  be  facilitated  by  re- 
ference to  the  diagram  (Fig.  2),  which  represents  the  field  of  fixation 
of  a  normal  eye  having  a  rather  extensive  power  of  motion. 

PROJECTION   OF   THE   FIELD  OF   FIXATION   AND   OF   THE 

FIELD  OF  ACTION  OF  EACH  OF  THE 

OCULAR  MUSCLES. 

C,  projection  of  extremity  of  line  of  sight  (point  of  fixation),  when 
eye  is  in  primary  position;  D,  E,  O,  projection  of  same  when  eye 
IS  abducted  18°.  30°,  and  50°,  respectively;  B,  A,  P,  projection  when 
eye  is  adducted  20°,  50°,  and  G0°,  respectively.  The  distance  CO 
represents  the  maximum  degree  of  excursion  of  the  eye  outward 
Most  of  this  movement  is  effective  by  the  e.rtenml  m7»s,  but  a  cerlain 
portion  especially  towards  the  outer  eud  of  the  excursion  is  accomplished 
by  the  united  action  of  the  two  obliques  (see  ivfra).  The  distance  CT 
represents  the  niaxinuiiii  range  of  excursion  of  the  eye  inward  This 
inward  movement  is  effected  mainly  bv  the  i»(ernal  rectus,  assisted 
especially  towards  the  eud  of  the  excursion  by  the  superior  and  inferior 
recti  (see  infra). 

The  black  lines  AA,,  15B,,  C(\.  1)D,.  EEi,  repre.sent  the  amount 
and  direction  of  the  movement  produced  by  the  superior  rectus  when 
the  eye  is  respectively  addncled  r>0^'  (A);  adducted  20«  (H);  j,,  the 
primary  position  (O)  ;  abducted  ]S-'  (D);  and  abducted  M0«  (K)  The 
red  lines  AAt,  BH,,.  CC,,.  1)1).,,  EE,,.  represent  the  amount  and  di- 
rection of  the  nioveiiient  eflfected  by  the  inferior  oblii/ue.  and  the 
(lotted  lines  AA,j,  BB.i,  CCa,  DDg,  EE3,  tJie  moveiuent  effected  by  the  in- 


NEW  CLASSIFICATION  OF  MOTOR  ANOMAI.ItS.  27 

ferior  oblique  and  the  superior  rectus  acting  together.  Similarly,  the 
black  lines  AA4,  IJB4,  ('C4,  1)1)4,  KK4  represent  the  lines  of  action  of  the 
inferior  rectus;  AA5.  BB5,  CC5,  DDs,  EEs,  those  of  the  superior  oblique; 
and  AAe,  BBg,  CCe,  DDq,  EEe,  those  of  the  two  latter  muscles  combined. 
The  heavy  black  lines  AiBiCiDiKi  and  A4B4C4D4E4  represent  the  limits  of 
the  Jiekls  of  action  of  the  superior  and  the  inferior  recti;  and  the  heavy 
red  lines,  A2B2C2D.2E..;  and  AftB^CsDsEs  the  limits  of  the  tields  of  action  of 
the  inferior  and  the  superior  obliques.  The  heavy  dotted  line  AePAaBs 
C3,  etc.,  represents  the  limit  of  ihQ  field  of  fixation. 

It  will  be  seen  from  the  diagram  how  the  vertical  (elevating  and 
depressing)  action  of  the  superior  and  inferior  recti  increases,  and 
how  the  vertical  action  of  the  obliques  decreases  progressively  as  the 
eye  is  carried  from  a  position  of  marked  adduction  (A)  to  one  of 
moderate  abduction  (E).  It  will  also  be  apparent  how  the  lateral 
action  of  each  of  these  muscles  diminishes  as  its  vertical  action  in- 
creases; so  that  the  adductive  power  of  the  superior  and  inferior 
recti  shows  a  progressive  diminution,  and  the  abduetive  power  of 
the  two  obliques  a  progressive  increase  as  the  eye  passes  from  A 
to  E.  That  is,  at  A  (i.  e.,  when  the  eye  is  adducted  50°)  the  superior 
;ind  inferior  recti  have  no  vertical  action  at  all,  but  simply  adduct 
the  eye  through  a  comparatively  large  extent,  while  the  two  oWiques 
liave  no  lateral  action  at  all,  but  simply  elevate  and  depress  the 
eye. 

At  E,  on  the  other  hand  (when  the  eye  is  abducted  30°),  the  two 
recti  no  longer  act  as  adductors  at  all,  but  simply  elevate  and  de- 
press the  eye;  and  the  two  obliques  no  longer  exert  any  vertical 
effect,  but  combine  to  carry  the  eye  outwards,  their  abduetive  action, 
in  fact,  being  here  at  its  maximum. 

At  A  the  superior  rectus  and  the  inferior  oblique  acting  together 
to  their  full  extent  will  cariT  the  eye  up  and  noticeably  inwards 
to  A3) ;  since  here  the  adductive  action  of  the  rectus  is  at  its  max- 
imum and  besides  is  not  balanced  by  any  opposing  abduetive  action 
on  the  part  of  the  oblique.  Similarly  at  E  the  two  muscles  acting 
together  will  carry  the  eye  upwards  and  noticeably  otttwards.  In  In- 
tel-mediate positions,  as  at  B  and  D,  the  lateral  action  of  one  muscle 
will  partially  counteract  that  of  the  other,  so  that  the  net  lateral 
effect  will  be  less.  E.  g.,  at  B  the  adductive  action  of  the  superior 
rectus  is  less  than  it  was  at  A  and  moreover  is  now  opposed  by  a 
moderate  abduetive  action  on  the  part  of  the  inferior  oblique,  so 
that  the  net  adductive  effect  is  but  slight.  The  eye,  therefore,  here 
is  carried  up  by  the  inferior  oblique,  assisted  somewhat  by  the 
superior  rectus,  and  is  also  carried  slightly  inwards  (to  B3).  At  D, 
on  the  contrary,  it  is  carried  upwards  mainly  by  the  superior  rectus, 
assisted  somewhat  by  the  inferior  oblique,  and  is  also  carried 
slightly  outwards  (to  D3),  by  the  preponderating  lateral  (abduetive) 
action  of  the  latter  muscle.  At  C  (the  primary  position)  the  adduc- 
tive action  of  the  superior  rectus  apparently  balances  the  abduetive 
action  of  the  inferior  oblique,  and  hence  the  etfeot  of  the  two  ele- 
vators acting  together  will  be  to  carry  the  eye  straight  upwards. 

In  a  similar  way  the  inferior  rectus  and  the  superior  oblique  acting  to- 
gether will  carry  the  eye  down  and  in  (AAe,  BBe) ,  down  and  out  (DDg,  EEk)  , 
or  straight  down  (CCe),  according  as  the  eye  is  already  adducted,  ab- 
ducted, or  in  the  primary  position. 

The  superior  or  inferior  rectus  actina  together  with  Just  sufficient 
force  to  neutralize  each  other's  vertical  action,  will  combime  to  ad- 
duct the  eye,  the  adducent  effect  being  forcible  at  A  ''=AAi4-AA4  or 
AA7),  and  diminishing  graduallv  to  E  where  it  is  zero.  At  E.  there- 
fore, i.  e..  when  the  eve  is  abducted  ."^O",  the  inferior  and  superior 


28  NEW    CLASSIFICATION  OV   MOTOK  ANOMALIES. 

recti  aetiugr  together  will  pi-oduce  no  movemeut  aud  beiice  in  this 
position  are  dii-ect  antagonists. 

Similarly  the  superior  and  inferior  oblirjnes  acting  together  neu- 
tralizes each  others'  vertical  action,  but  combine  to  abduct  the  eye. 
The  abducent  effect  is  greatest  at  E  (=  EE2+EEo=KE8j,  aud  dimin- 
ishes progressively  to  A,  where  it  is  zero.  In  tlie  latter  position,  there- 
fore, i.  e.,  when  the  eye  is  abducted  50°,  the  two  obliques,  acting  simply 
to  elevate  and  depress  the  eye  respectively,  are  direct  antagonists. 

The  four  muscles,  superior  atid  inferior  recti  and  superior  and  in- 
ferior oblii/nes  acting  together  with  ihe  force  required  to  neutralize 
each  other's  vertical  action,  will  produce  a  lateral  efltect  varying 
with  the  amount  by  which  the  eye  is  already  abducteil  or  adductcd. 
Thus  if  the  eye  is  already  adducted  50°  (to  A),  a  position  in  which 
the  obliques  exert  no  lateral  action  at  all,  the  total  effect  of  tlu' 
four  muscles  will  be  to  carry  the  eye  quite  a  little  distance  further 
inward  (to  At).  If  the  eye  is  adducted  only  'M^  (B),  the  resultant 
action  of  the  four  muscles  will  be  the  difference  between  the  adduc- 
tive  action  of  the  two  recti  (BB7),  and  the  less  marked  abducent 
action  of  the  two  obliques  (UBs);  i.  e.,  the  eye  will  be  adducted 
slightly  (to  IJy).  At  C  (the  primary  povsition),  the  abducent  action 
of  the  obliques  balances  the  adducent  action  of  the  superior  aud  in- 
ferior recti,  so  that  the  contraction  of  the  four  muscles  will  causi- 
the  eye  to  remain  stationary.  At  D,  on  the  contrary,  the  abductive 
effect  will  preponderate  somewhat,  and  the  eye.  already  abducted 
18",  will  be  carried  still  further  moderately  outward<  (to  \h).  At  E. 
i.  e.,  when  the  eye  is  abducted  30°,  the  abducent  effect  is  stiil  more 
pronounced  (=  EEs). 

It  is  thus  apparent  that  if  all  four  muscles  act  together  they  will, 
if  the  eye  is  being  adducted  or  abducted,  tend  to  carry  it  still  further 
in  the  direction  in  which  it  is  goinq.  They  will,  therefore,  reinforce 
the  external  rectus  in  abducting  and  the  internal  rectus  in  adductiui: 
the  eye,  aud  tlie  amount  of  the  reinforcement  will  increase  in  propor- 
tion as  the  eye  is  already  abducted  or  adducted.  So  that  the  in- 
ternal rectus,  for  example,  when  it  begins  to  contract  (i.  e..  is  just 
leaving  the  primary  position  at  C)  will  receive  little  or  no  aid  from 
the  contraction  of  the  other  four  muscles,  but.  as  it  continues  to  act. 
(e.  g.  at  B).  will  be  more  and  more  assisted  by  them,  and  finally 
when  it  reaches  the  limit  of  its  contraction  (at  A)  and  is  consequently 
working  at  a  great  mechanical  disadvantage,  will  be  strongly  rein- 
forced. In  like  manner  the  external  rectus  will,  as  its  own  etticiency 
diminishes  with  the  increasing  abduction  of  the  eye,  be  assisted 
more  and  more  by  the  simultaneous  contraction  of  the  other  mus- 
cles. And  it  is  altogether  probable  that  it  is  in  this  way  that  the 
outward  and  inward  excursion  movements  of  the  eye  are  rendered 
regular  and  uniform.* 


*It  may  be  noted  that  the  action  c*f  the  superior  and  inferior  recti 
in  compensating  for  an  increasdng  feeblenes.s  of  the  internal  rectus 
is  shown  in  another  way  also.  The  internal  rectus,  as  Weiss  has 
])oiu(('d  out  (.\rch.  f.  Augenheilk;  Vol.  xxix).  acts  very  much  mori' 
feebly  when  llic  divergence  of  the  orbits  is  great,  i.  e..  when  the  orbits 
:ire  sli:illi>w  and  the  eyes  far  apart.  Rut  it  is  under  just  these  condi- 
tions that  tlie  sujierior  iiud  inferior  recti  act  to  most  advautjige  as  ad- 
ductors, .-^iiice.  the  gre:iter  the  divergeiic(>  of  the  orbits,  the  greater 
Ihe  angle  wliich  the  line  of  action  of  tliese  two  nmscies  nutkes  witii 
tlie  aiitero-i>osterior  axis  of  tlu>  eye.  and  tlie  greater  tMUsequently  is 
tlie  l;iier;il  effecl    which  tliev  ar(>  able  to  (>xi'rt. 


NEW  CLASSIFICATION  OF  MOTOR  ANOMALIES.  29 

Our  diagram  may  also  be  used  to  illustrate  the  action  of  the  as- 
sociated antayonists.  If  alongside  of  Fig.  3,  which  represents  the 
Held  of  axatiuu  of  the  right  eye,  we  place  one  representing  the  field 
of  fixation  of  the  left  eye  (which  may  be  done  by  turning  Fig.  3 
end  for  end,  so  that  O  is  on  tlie  left  and  P  on  the  right  of  the  figure), 
we  shall  see  how  the  field  of  action  (A2B.2C2D2E2),  of  tlie  in- 
ferior oblique  of  the  right  eye  agrees  in  all  respects  with  the  field 
of  action  of  the  superior  rectus  of  the  left  eye.  So  also  of  the  other 
associated  antagonists  (R.  superior  rectus  and  L.  inferior  oblique;  R. 
inferior  rectus  and  L.  superior  oblique;  R.  superior  oblique  and  L. 
inferior  rectus). 

Another  point  elucidated  by  the  diagram  is  the  amount  and  kind 
of  torsion  movement  (rotation  of  vertical  meridian  of  the  cornea) 
produced  by  the  various  muscles.  That  is  the  Hue  BBi  represents 
the  fact  that  when  the  eye  is  adducted  to  B  the  superior  rectus 
will  not  only  carry  the  eye  itself  upwards  and  inwards  (to  Bi),  but 
will  also  rotate  the  vertical  meridian  of  the  cornea  so  that  the  latter 
will  have  the  inclination  BBi,  i.  e.,  will  be  inclined  inwards.  In  a 
similar  way,  the  inferior  oblique  in  the  same  situation  will  not  only 
carry  the  eye  upwards  and  outwards  (to  B2),  but  will  also 
rotate  the  vertical  meridian  of  the  cornea  outwards,  so  that  it  will 
have  the  direction  BB2.  And  the  combined  action  of  the  two  muscles 
will  be  to  give  the  vertical  meridian  the  inclination  BB^,  i.  e.,  one 
of  slight  rotation  inwards.  So  also  BBe  represents  the  inclination 
of  tlie  vertical  meridian  of  the  cornea  (viz.,  with  the  upper  end 
rotated  inwards),  when  the  eye  is  carried  do'wnwards  from  a  position 
of  adduction  (B).  Again,  the  fact  that  CC3  is  strictly  vertical  shows 
that  when  the  eye  is  in  the  primary  position  it  is  not  only  carried 
straight  upw-ards  by  the  combined  action  of  the  two  elevators,  but 
its  vertical  meridian  also  remains  vertical  during  the  ascent. 

It  will  also  be  observed  that  the  combined  action  of  the  superior 
and  inferior  recti  or  of  the  superior  and  inferior  obliques,  or  of  all 
four  muscles  together  will  be  not  only  to  keep  the  eye  in  the  hori- 
zontal plane  (in  the  line  OP),  but  also  to  keep  its  vertical  meridian 
from  rotating  either  to  the  right  or  to  the  left,  as  the  eye  is  carried 
outwards  or  inwards.* 

In  fact,  all  the  various  applications  of  the  laws  of  Bonders  and 
Listing  may  be  deduced  from  the  study  of  thisi  diagram. 

Finally  the  diagram  shows  the  limitation  of  the  field  of  fixation 
and  the  kind  and  amount  of  diplopia  present  in  paralysis  of  any 
one  of  the  ocular  muscles.  Suppose,  for  example,  that  the  superior 
rectus  is  paralyzed.  Then  the  field  of  fixation  while  normal  below, 
will,  since  the  inferior  oblique  is  the  only  elevator  left,  he  repre- 
sented above  not  by  A3B3C3D3E3,  but  by  A2B2C2D2E>.  In  other  words, 
when  the  attempt  is  made  to  elevate  the  eye  as  far  as  possible,  it  will 
stand  at  A2,  instead  of  A3,  at  B2,  instead  of  B3,  etc.  Since  its  fellow  eye 
has  a  normal  field  of  fixation  and  hence  under  the  same  conditions  rises 
to  A3,  B3,  etc.,  the  difference  in  position  of  the  two  eyes  and  conse- 
quently also  the  amount  and  kind  of  diplopia  produced  will  be  repre- 
sented by  the  difference  between  A2  and  A3,  Bo  and  B3,  etc.  The  diagram 
thus  gives  us  a  graphic  representation  of  the  fact  that  in  paralysis  of  the 

*E.  g.,  at  C  the  inward  rotation  of  the  vertical  meridian  produced 
by   the  superior   rectus   will   be   represented   by   the   angle  C3CC2;  this 

inward  rotation  will  be  neutralized  by  the  equal  outward  rotation 
CeCC^,    produced    by    the    inferior    rectus:    and    hence    the    combined 

effect  of  these  two  muscles  will  be  to  keep  the  vertical  meridian 

from  rotating  either  one  way  or  the  other. 


30  \i;\V  CLASSIFICATION  OK   MOTOR  ANOMALIES. 

superior  rectus  the  vertical  diplopia  increases  rapidly  when  the  eye  is 
carried  upwards  and  outwards,  wliile  the  lateral  (crossed)  diplopia  in- 
creases as  the  eyes  are  carried  upwards  and  inwards. 

The  diagram  may  also  be  utilized  to  map  out  the  field  of  fixa- 
tion in  cases  of  combined  paralyseK.  Thus  the  Held  of  fixation  iu  a  case 
of  paralysis  of  both  the  superior  rectus  and  the  superior  obliciue  would 
be  represented  by  AoB.)02D.jE2K4l)4C4B4A4;  and  in  a  combined  paralysis 
of  the  superior  and  inferior  rectus  by  AoBjCaDoE-iD.'iCsBsAs. 

III. 

THE  TESTS  EMPLOYED  AND  THEIR  SIGNIFICANCE, 

The  object  of  the  various  tests  that  we  make  use  of  is  to  deter- 
mine the  following  data : 

(1).  The  precision  and  steadiness  with  which  binocular  fixa- 
tion is  effected  (Static  Tests). 

(2).  The  ability  of  the  eyes  to  move  in  various  directions 
while  still  maintaining  binocular  fixation  (Dynamic  Association- 
tests). 

(3).  The  ability  of  the  eyes  voluntarily  to  deviate  from  the  po- 
sition of  binocular  fixation  (Dynamic  Disassociation-tests). 

These  tests  may  be  performed  both  for  distance  (with  the  vis- 
ual lines  parallel)  and  for  near  (with  the  visual  lines  converged). 

The  chief  tests  for  binocular  fixation  are  : 

(1).  Inspection  with  both  eyes  uncovered.  This  gives  us 
an  approximate  idea  as  to  whether  both  eyes  are  directed  at  the 
same  object,  a  non-fixing  eye  appearing  to  deviate  in,  out,  up. 
or  down,  according  to  circumstances. 

In  making'  this  test  we  must  be  careful  not  to  be  misled  by  the 
presence  of  a  large  angle  alpha,  which  may  simulate  a  deviation  where 
none  exists.  Any  error  on  this  score  will  be  prevented  by  compar- 
ing the  findings  with  those  of  the  screen  test;  for  a  deviation,  great 
enough  to  be  noticeable  upon  simple  inspection,  will  eertaiuly  give 
evidence  of  its  presence  by  a  distinct  movement  of  the  eyes  when 
the  cover  is  shifted  from  one  eye  to  the  other. 

(2)  Fixation  and  Diplopia  Tests.  A  patient  with  normal 
eyes  and  perfect  l)inocular  fixation,  will  see  distinctly  with  either 
eye  alone,  or  with  both  together,  and  will  also  see  single.  If 
either  eye  or  both  fail  to  fix  the  object  looked  at,  that  object 
will  appear  blurred  (Fixation-test),  and  if  one  eye  fixes  and  tlie 
other  docs  not,  the  patient  will  in  general  see  double  ( Diplopia- 
test),  the  image  of  the  fixing  eye  being  clear  and  that  of  the 
other  more  or  less  shadowy  and  indistinct.  The  kind  of  diplopi:> 
present  indicates  the  nature  of  the  deviation.  Thus  an  /toniony- 
inous  diplopia  (i.  e.,  one  in  which  the  image  formed  by  the 
right  eye  is  on  the  right  side,  and  that  formed  by  the  left  e\e  imi 


NEW  CLASSIFICATION  OK  MOTOR  ANOMALIES. 


:n 


the  left  side)  signifies  abnormal  converg-ence  of  the  visual  lines; 
a  crossed  or  hetcronyvious  diplopia  (in  which  the  image  of  the 
right  eye  is  on  the  left  side  and  vice  versa)  signifies  lateral  di- 
vergence;  and  vertica/  diplopia  (in  which  one  image  is  higher 
than  the  other)  signifies  vertical  separation  of  the  visual  lines, 
so  that  one  is  higher  than  the  other.  The  last-named  variety 
may  be  further  differentiated  into  right  diplopia,  in  which  the 
image  formed  by  the  right  eye  is  below  (indicating  the  condi- 
tion in  which  the  right  visual  line  is  the  higher),  and  left  diplo- 
pia^ in  which  the  contrary  conditions  prevail. 

The  amount  of  diplopia  is  precisely  proportional  to  the  amount 
of  deviation.  It  may  be  measured  either  by  estimating  the  linear 
distance  between  the  two  images,  the  distance  of  the  object 
looked  at  being  also  known,*  or  by  determining  the  strength  of 
the  prism  which  appropriately  placed,  will  correct  the  diplopia.f 
In  order  to  differentiate  the  double  images  it  is  convenient  to 
use  a  light  as  a  test-object,  and  have  a  red  glass  placed  before 
one  of  the  eyes.  By  thus  giving  the  two  images  a  different  colort 
we  enable  the  patient  the  better  to  distinguish  between  the  two 
and  recognize  the  fact  that  diplopia  exists;  and,  moreover,  since 
the  red  flame  must  belong  to  the  eye  covered  with  the  red  glass, 
we  can  determine  from  the  patient's  statements  as  to  the  relative 
place  of  the  red  and  white  images,  whether  we  are  dealing  with 
homonymous  or  crossed  (lateral)  or  with  right  or  left  (vertical) 
diplopia. 

(3)  Equilibrium  Test.  This  is  simply  a  variety  of  the  diplo- 
pia test.  It  consists  of  two  steps.  In  the  first  an  artificial  ho- 
monymous diplopia  is  produced  by  means  of  a  prism  of  12°  or 
more,  placed 'base  in,  before  the  eyes.  If  the  two  images  thus 
produced  are  on  a  level,  the  visual  lines  themselves  are  on  a  level. 
If,  however,  the  right-hand  image  should  be  lower,  there  is  really 
a  natural  right  diplopia  present  in  addition  to  the  artificial  ho- 
monymous diplopia,  i.  e.,  the  right  visual  line  is  higher,  or,  to  use 
Stevens'  nomenclature,  there  is  right  hyperphoria.     The  amount 

*A  linear  distance  of  1"  between  the  images  is  equivalent  to  a 
deviation  of  li/o°  in  the  visual  lines  when  the  test-object  is  1  metre 
distant  and  to  i/i°  when  the  latter  is  20  feet  distant. 

tA  prism  rarely  measures  the  full  amount  of  the  diplopia,  a-s  a 
prism  which  slightly  undereorrects  the  latter  nevertheles)S  brings 
the  double  images  so  close  together  that  the  residual  correction  can 
be   and  is  effected  by  the  eyes  themselves. 

JA  similar  difference  in  character  may  be  imparted  to  the  images 
by  placing  a  Maddox  rod  or  a  Stevens'  sphere  before  one  eye;  but 
the  red  glass  is  simpler  and,  in  comparison  with  the  Maddox  rod 
at  least,  is  less  confusing  to  the  patient  and  less  apt  to  give  am- 
biguous results. 


32  NEW  CLASSIFICATION  OK   .MOTOI{  ANOMALIES. 

of  this  latter  may  be  measured  by  the  degree  of  prism,  which, 
placed  base  down  before  the  right  eye,  will  rectify  the  diplopia, 
i.  e.,  will  bring  the  images  on  a  level.  In  the  next  step  of  the  test, 
a  strong  prism  is  placed  base  down  before  the  right  eye,  produc- 
ing a  marked  vertical  (left)  diplopia.  If  both  eyes  are  properly 
adjusted  for  the  object  of  fixation,  the  two  images  will  be  in  a  ver- 
tical line.  If,  however,  the  upper  image  is  to  the  right  of  the 
lower,  there  is  really,  besides  the  artificial  vertical  displacement, 
a  natural  homonymous  diplopia,  or,  to  use  Stevens'  expression, 
there  is  an  esopJioria.  Similarly,  if  the  upper  image  is  to  the  left 
of  the  lower,  there  is  really  a  crossed  diplopia  or  cxophoria.  In 
either  case  the  amount  of  the  esophoria  or  exophoria  may  be 
measured  by  the  strength  of  the  prism  which,  placed  base  out  or 
base  in  will  rectify  the  diplopia,  i.  e.,  will  bring  the  two  images 
into  a  vertical  line. 

In  Stevens'  phoTometer,  which  is  the  best  instrument  for  this  pur- 
pose, the  measurement  of  the  deviation  is  effected,  not  by  placing 
additional  prisms  before  the  eyes,  but  \>j  revolving  the  prism  that 
lias  been  used  to  produce  the  initial  latea'al  or  vertical  diplopia  until 
the  images  are  truly  horizontal  or  vertical.  The  amount  of  rota- 
tion is  read  off  on  an  arc  graduated  so  as  to  indicate  directly 
the  amoimt  of  hyperphoria,  esophoria,  or  exophoria  present* 

One  defect  of  the  equilibrium  test  is  that  patients  often  try  in- 
voluntarily to  bring  the  two  images  into  line  and  thus  appear 'to 
have  no  deviation  of  the  visual  lines,  although  one  actually  exists. 
On  the  other  hand,  the  involuntai-y  movements  set  up  in  the  attempt 
made  to  compare  two  similar  images  placed  at  a  distance  from  each 
other  may  cause  a  deviation  to  be  simulated  where  none  is  present. 
I  have  seen  this  occur  not  infrequently— sometimes  to  a  very  marked 
degree.  The  equilibrium  test  being  thus  apt  to  set  up  a  certain 
amount  of  muscular  tension  and  hence  disturb  the  tnie  relation  of 
the  visual  lii-es,  is  in  actual  practice  best  performed  after  the  tests 
next  to  be  described  in  which  the  eyes  are  under  more  normal 
conditions. 

(4)  Screen  Test.  This  depends  upon  the  fact  that  the  ten- 
dency to  binocular  fixation  is  so  strong  that  it  still  persists,  even 
when  one  eye  no  longer  sees  the  object  of  fixation.  If,  therefore, 
a  card  be  placed  before  the  left  eye,  and  the  gaze  be  directed  at 
a  distant  object,  the  left  eye  will,  in  case  there  is  no  disturbance 
of  innervation  causing  it  to  deviate,  look  straight  at  the  object, 
just  as  if  the  latter  were  still  visible.  If  now  the  card  is  shifted 
from  the  left  eye  to  the  right,  the  former  being  already  properly 
directed,  will  not  have  to  change  position  in  order  to  fix  the  ob- 

♦The  same  thing  may  readily  be  done  with  the  ordinary  trial- 
frame,  if  we  use  in  it  a  12°  prism  and  recollect  that  with  this 
each  rotation  of  5°  from  the  horizontal  represents  1°  of  hyperphoria, 
and  each  rotation  of  5°  from  the  vertical  1°  of  esophoria  or  ex- 
ophoria. 


NEW  CLASSIFICATION  OF   MOTOR  ANOMALIES. 


33 


ject,  and  will  hence  remain  stationary.  If,  however,  the  left  eye 
when  screened,  deviates  in  any  way,  e.  g.  outward,  it  will,  when 
the  screen  is  transferred  to  the  right  eye,  have  to  turn  inward,  or 
to  the  right,  in  order  to  fax  the  object,  and  the  amount  of  its  ex- 
cursion inward  (movement  of  redress)  will  be  precisely  equal  to 
the  amount  of  its  previous  deviation.  At  the  same  time  that  the 
left  eye  turns  inward,  or  to  the  right,  in  order  to  perform  fixation, 
the  right  eye,  which  is  now  covered  by  the  card  and  which,  ac- 
cording to  the  law  of  associated  parallel  movements,  receives  an 
impulse  to  move  to  the  right  equal  to  that  communicated  to  the 
left  eye,  will  move  outward. 

Whether  it  moves  outward  to  the  same  extent  that  the  left  eye 
moves  in  or  not,  depends  upon  the  relative  ability  of  the  muscles 
of  the  two  eyes  to  respond  to  the  stimulus  imparted  to  them.  If, 
for  instance,  the  left  interuus  is  weak  (paretic)  a  very  strong  impulse 
will  be  required  in  order  to  make  the  muscle  contract  enough  to 
cause  the  eye  to  move  in  to  the  proper  extent.  According  to  the 
law  of  association,  an  equally  powerful  impulse  will  be  communi- 
cated at  the  same  time  to  the  right  externus;  and,  if  the  latter  is 
normally  strong,  it  will  respond  much  more  efficiently  to  this  im- 
pulse than  did  the  weak  internus  of  the  other  eye,  and  will,  con- 
sequently, carry  the  right  eye  out  much  further  than  the  left  eye 
was  caiTied  in. 

It  may  be  stated  as  a  general  rule  (to  which,  however,  there  are 
not  a  few  exceptions)  that  in  concomitant  deviations  the  deflec- 
tion behind  the  screen,  and  hence  also  the  movement  of  redress 
that  the  eye  makes  when  the  screen  is  removed,  are  equal  for. 
the  two  eyes,  and  that  in  non-concomitant  deviations  they  are 
unequal,  being  greater  in  the  eye  which  has  the  more  powerfully 
acting  muscles. 

The  screen  test  may  also  be  used  to  ascertain  ivhich  oj  th 
two  eyes  habitually  fixes. 

In  doing  this  the  screen  instead  of  being  shifted  from  one  eye 
to  the  other  is  simply  removed  from  the  eye  before  which  it  is  placed, 
leaving  both  eyes  uncovered.  Each  eye  under  these  circumstances 
will  deviate  when  the  screen  is  in  front  of  it,  and  the  other  eye 
will  fix.  If  now  the  eye  that  is  behind  the  screen  is  the  one  that 
in  binocular  vision  is  regularly  employed  for  fixation,  it  will  move 
into  the  position  of  fixation  as  soon  as  the  screen  is  taken  away, 
and  the  other  eye  will  deviate.  If,  however,  the  eye  that  is  behind 
the  screen  does  not  ordinaTily  perform  fixation,  it  will  not  move 
when  unscreened,  and  the  other  eye  will  continue  to  fix,  i.  e.,  will 
remain  steady  in  its  place.  That  lis,  the  fact  that  the  eyes  perform 
a  movement"  of  redress  when  the  right  is  unscreened  and  both  are 
left  open  indicates  that  the  right  eye  haibitually  fixes.  If  no  move- 
ment takes  place,  when  the  right  eye  is  unscreened,  the  latter  can 
not  be  the  eye  that  habitually  fixes;  and  if  no  movement  takes  place 
when  the  right  eye  and  the  left  alternately  are  unscreened,  there 
must  be  an  alternating  deviation,  i.  e.,  one  in  which  either  eye  in- 
differently is  used  to  fix  with. 
3 


34  NEW  CLASSIFICATION  OF  MOTOR  ANOMALIES. 

The  amount  of  deviation  behind  the  screen,  or  of  the  move- 
ment of  redress  made  by  the  eye  from  which  the  screen  has  been 
removed,  may  be  roughly  estimated  by  marks  made  upon  the  Hds 
or  may  be  more  accurately  determined  with  the  perimeter  or  by 
some  of  the  various  strabometric  methods  which  have  been  well 
described  by  Maddox  (  A rchivcs  of  Op/it/i.,  XXL ,  1 ,  1892).  An 
angular  deviation  of  l°-2°  is  generally  sufficient  to  produce  a 
noticeable  deviation  behind  the  screen. 

Finally,  it  must  be  n  >ied  that  the  sci-een  test  is  valueless  U7iless 
the  patient  can  be  got  to  Jix  with  the  uncovered  eye.  Hence,  the 
test  is  of  no  service  in  those  who,  owing  to  a  deviation  of  long 
standing,  have  lost  the  power  of  fixation;  and  it  may  likewise 
prove  nugatory  in  children  who  fail  to  keep  their  gaze  directed 
at  the  object  that  they  are  told  to  look  at. 

(5)  Parallax  Test.  When  the  screen  test  is  employed,  the 
patient,  if  his  eye  deviates  behind  the  screen,  will  in  general  no- 
tice a  movement  of  the  object  whenever  the  screen  is  shifted. 
This  movement  is  called  the  parallax^  and,  if  the  test-object  is  so 
placed  as  not  to  be  projected  upon  any  surface  back  of  it  (e.  g.,  if 
it  is  a  spot  upon  a  blank  wall),  furnishes  a  valuable  indication  of 
the  amount  and  character  of  the  deviation.  The  perception  of 
this  movement  is  really  nothing  but  the  perception  of  a  diplopia, 
which  differs  from  ordinary  diplopia  in  the  fact  that  the  t^vo  im- 
ages are  seen  in  succession^  instead  of  at  the  same  ti/ne,  and,  as 
they  occupy  different  places,  give  the  impression  of  a  single  im- 
age which  has  moved  from  one  place  to  another.  Thus,  if  there 
is  convergence  (esophoria),  the  right  eye,  when  unscreened,  and 
before  it  has  had  a  chance  to  assume  the  position  of  fixation,  sees 
the  object  a  little  further  to  the  right  than  the  left  eye  saw  it,  i.  e., 
the  object  appears  to  have  moved  from  left  to  right  (homony- 
mous parallax).  If,  on  the  other  hand,  there  is  divergence  (ex- 
ophoria),  the  right  eye  will  when  unscreened  see  the  object  a 
little  further  to  the  left  than  the  left  eye  did  when  it  was  fixing, 
i.  e.,  the  object  appears  to  have  moved  from  \\^\iio\G.ii( crossed 
parallax).  So,  too,  right  hyperphoria  is  indicated  by  the  fact 
that  the  object  appears  to  move  down  when  the  right  eye  is  un- 
covered (right  parallax),  while  in  left  hyperphoria  the  object 
seems  to  move  up  (left  parallax).  These  various  movements  are 
noticeable  even  when  the  deviation  is  verv  slight;  a  hvpcrplioria 
of  0.1",  for  example,  being  made  ajipreciable  bv  a  distinct  up 
and  down  movement  of  the  object. 

The  amount  of  the  parallax  may  be  measured  by  the  strength 
of  the  prism  which,  placed  before  the  eyes,  will  neutralize  the 


NEW  CLASSIFICATION  OF  MOTOR  ANOMAMKS. 


35 


movement.  Homonymous  parallax  will  be  neutralized  by  a 
prism  base  out,  a  vertical  parallax  by  a  prism  with  the  base  up  or 
down,  etc.  The  fact  of  neutralization  or  reversal  is  generally  in- 
dicated by  the  patient  with  great  precision. 

Tests  for  the  Associated  Parallel  Movements.  The  ability 
of  the  eyes  to  perform  associated  parallel  movement^,  i.  e.,  the 
range  through  which  they  can  move  in  any  direction  and  still 
car'ry  on  binocular  fixation,  is  tested  in  the  same  v^  ay  as  the  abil- 
ity to  maintain  binocular  fixation  while  in  the  primary  position. 
All  the  tests  just  described  are  applicable.  Thus  inspection  en- 
ables us  to  say  whether  the  movement  of  the  eyes  in,  out,  up,  or 
down,  is  too  slight  or  too  excessive;  also  the  point  where  one  eye 
ceases  to  keep  up  with  the  other,  this  being  shown  by  the  fact 
that  the  former  visibly  lags  behind  or  wavers  in  its  course.  In: 
this  way  we  may  map  out  the  monocular  ox  bi)iocular  field  of  fix- 
ation, as  may  also  be  done  more  accurately  by  the  fixation  test 
(with  the  double  dot,  as  already  described).  So,  too,  by  the 
diplopia  test  we  m-A}^  out  ihe  field  of  binocular  single  vision,  and 
thus  also  determine  whether  the  eyes  follow  each  other  to  a  nor- 
mal extent  or  not.  With  the  same  object  in  view  we  apply  the 
screen,  parallax,  and  equilibrium  tests  to  ascertain  if  there  is 
any  visible  deflection,  parallactic  movement,  or  heterophoria 
within  the  limits  of  the  normal  field  of  fixation,  and,  if  so,  where 
they  begin,  and  in  what  direction  they  increase. 

By  these  various  means  we  determine  whether  the  n?ovenicnis 
in  any  given  direction  are  excessive  or  restricted.  In  this  re- 
gard, inspection  and  the  diplopia  and  screen  tests  are  practically 
the  most  applicable.  The  mapping  out  of  the  field  of  fixation  is 
laborious  and,  for  the  reasons  already  given,  the  results  obtained 
are  very  uncertain,  unless  a  series  of  examinations  upon  the  same 
patient  happen  to  be  quite  concordant. 

On  the  other  hand,  the  diplopia  test  is  readily  applicable,  and  in 
my  experience  gives  much  more  constant  and  reliable  results.. 
Diplopia  may,  to  be  sure,  occur  normally,  as  a  transient  phenom- 
enon (physiolrgical  diplopia)  in  most  people  when  the  gaze 
is  carried  far  towards  the  periphery  of  the  field  of  fixation ;  but 
such  diplopia,  as  already  stated,  is  inconstant  and  superable  by 
voluntary  effort.  A  diplopia  occurring  under  all  circumstances 
as  soon  as  the  gaze  has  been  carried  from  35°  to  40°  from  the 
primary  position,  in  any  given  direction,  indicates  an  abnormal 
weakness.  This  again  may  be  temporar}-,  and  a  diplopia  of 
this  sort  occurring  about  equallv  far  in  all  tlirections  from  the 
periphery  (concentric  contraction  of  the  field  of  single  vision) 


36  NKW  CLASSIKICATION  uF   MO  I  OK  ANOMALIES. 

indicates  a  temporary  enfeeblenient  of  all  the  ocular  muscles 
such  as  may  happen  in  neurasthenia  and  form  one  of  the  evi- 
dences of  a  general  depression  of  the  muscular  forces.  On  the 
other  hand,  a  diplopia,  insuperable  by  voluntary  efifort  and  con- 
stantly occurring  as  soon  as  the  gaze  is  carried  30°  or  less  in 
any  given  direction  from  the  primary  position,  indicates  a  true 
weakness  or  paresis,  of  some  one  of  the  ocular  muscles  (paretic 
diplopia).  The  differential  diagnosis  of  this  condition,  based 
upon  the  character  of  the  diplopia,  will  be  touched  upon  later. 

Tests  for  Convergence.  The  tests  for  binocular  fixation  in 
convergence  are  the  same  as  those  for  distance,  namely,  inspec- 
tion, the  fixation  and  diplopia  tests,  the  screen  and  parallax  tests, 
and  the  equilibrium  test.  All  of  these,  in  fact,  are  habitually  ap- 
plied with  the  test-object  held  at  the  ordinary  reading  distance, 
as  well  as  at  a  distance  of  20  feet.  The  test-object  itself  for  the 
examination  at  near  points  should,  as  Randall  has  well  said,  be 
something  requiring  accurate  fixation  (e.  g.  a  pen-point  or  fine 
dot,  mstead  of  the  finger  which  is  habitually  used).  In  determin- 
ing the  parallax,  some  device  such  as  a  dot  on  a  large  card,  which 
does  not  allow  the  test-object  to  be  projected  upon  any  surface 
beyond  it,  should  be  employed. 

It  must  be  borne  in  mind  that,  while  orthophoria— absence  of 
deviation — is  the  ideal  state  for  distance,  a  slight  amount  of  di- 
vergence is  physiological  for  near.  Thus,  in  testing  at  12",  we 
expect  to  find  with  the  phorometer  an  exophoria  of  3°  to  0°, 
and  with  the  screen  a  crossed  parallax  of  the  same,  or  a  somewhat 
less  amount;  and  orthophoria  at  this  range  is  actually  to  be  re- 
gf'.rded  witi'  suspicion,  as  probably  indicating  an  undue  tendency 
to  convergence.  This  fact  does  not  militate  against  the  exist- 
ence in  these  cases  of  true  binocular  fixation  for  reading, or  other 
occupations  requiring  precise  adjustments. 

The  tests  for  the  associated  movements  in  conveigence,  like- 
wise are  made  in  the  same  way  as  for  the  associated  movements 
at  a  distance.  In  making  the  diplopia  test  at  near  it  is  best,  if 
using  the  candle,  to  hold  the  latter  not  less  than  30''  from  the 
eyes,  so  as  to  reduce  as  much  as  possible  the  effects  of  projection. 
If  it  is  desired  to  determine  the  field  of  binocular  single  vision 
for  closer  ranges,  the  effects  of  projection  may  be  obviated  by 
using  for  a  test-object  a  dot  on  a  large  card,  the  latter  being  tilted 
sc;  as  ahvays  to  be  perpendicular  to  the  patitnt's  line  of  sight. 

A  further  important  fact  to  determine  in  testing  movements  of 
convergence  is  the  convergence  near-point  (Pc).  This  is  ascer- 
tained by  rnrrying  a  fine  object  nearer  and  nearer  to  the  eyes,  un- 


JEW  CLASSIFICATION  OK  MOTOR  ANOMALIES. 


37 


til  tlio  latter  can  no  longer  be  converged  upon  it,  or  until  it  ap- 
pears double.  The  distance  of  the  object  from  the  root  of  the 
nc5-e  may  then  be  measured.  Notice  at  the  same  time  should 
be  taken  as  to  which  eye  is  the  first  to  deviate  when  the  limit'of 
convergence  is  reached.  The  same  test  should  be  repeated  from 
either  side,  the  object  of  fixation  being  first  placed  at  some  point 
A  to  the  right  of  the  middle  line  and  then  carried  directly  towards 
the  left  eye  L.  The  latter  obviously  will  not  have  to  change  its 
position  of  rdduction,  but  the  right  eye,  R,  in  order  to  follow  the 
object,  must  swing  inwards  through  a  considerable  arc,  A  C  P. 
If,  on  repeating  the  test  with  the  left  eye,  one  of  the  two  is  found 


Fig.  3. 


to  sag  off  from  the  test-object  much  sooner  than  the  other  eye 
does,  the  former  must  have  a  relatively  weak  adducting  power. 

Not  only  the  distance  of  the  convergence  near-point,  but  also 
the  ability  of  the  eyes  to  maintaiii  convergence  at  this  distance, 
should  be  noted. 

Lastly,  the  C'liwergence  must  be  tested  by  determining  the 
maximum  strength  of  prism  placed  base  out  before  the  eyes, 
which  the  latter  can  overcome  when  looking  at  a  distant  object. 
Usually,  if  the  patient  can  at  the  outset  overcome  a  prism  of  20° 
refracting  angle,  with  ease,  w-e  assume  that  he  could  readily  learn 
to  do  two  or  three  times  as  much  if  sufificiently  exercised,  and  we 
consider  his  prism-convergence  as  normal.  Exceptionally,  es- 
pfcially  in  cases  of  convergence-insufficiency,  w^e  find  that  the 


38  NEW  CLASSIFICATION  OF   MOTOR  ANOMALIES. 

prism-convergence  even  after  repeated  trials  cannot  be  got 
above  10°  or  12°  (prism),  and  that  even  this  amount  is  hard  for 
the  palient  to  do  and  still  harder  to  maintain. 

As  the  exercise  of  the  prism-convergence  not  infrequently  be- 
gets a  condition  of  convergence-spasm,  it  is  generally  best  to  de- 
fer testing  the  convergence  in  this  way  until  after  the  divergence 
has  been  determined. 

1 1  is  well  in  testing  the  convergence  by  means  of  adducting 
prism  to  ascertain  hoxv  in7ich  accommodation  the  patient  is  as- 
sociating with  it.  This  can  be  done  by  using  the  test-types  for 
the  object  of  fixation  and  finding  what  concave  glass  is  required 
to  give  the  patient  full  sight.  It  will  generally  be  found  that  by  re- 
peated practice  with  an  object  of  this  sort,  the  strength  of  the 
concave  glass  can  be  gradually  diminished — i.  e.,  the  patient 
gradually  acquires  the  ability,  when  looking  at  a  distant  object, 
to  converge  without  using  his  accommodation.  A  case  in  which 
extreme  facility  in  this  respect  was  acquired  has  already  been 
spoken  of.  It  is  often  important  therapeutically  to  efifcct  a  dis- 
association  of  this  sort  between  accommodation  and  convergence, 
especially  in  cases  of  convergence-insufficiency. 

Tests  for  Divergence.  The  diverging  power  is  determined 
by  the  amount  of  jjrism  placed,  base  in,  before  the  eyes,  which 
the  latter  can  overcome  when  looking  at  a  distant  object.  The 
strength  of  prism  thus  overcome  varies  in  normal  cases  from  G° 
to  8°  (refracting  angle).  A  divergence  of  less  than  5°  (prism) 
means  insuflficiency,  and  one  of  over  9*^  an  excess  of  diverging 
action. 

Tests  for  Sursumvergence.  The  sursumvergence,  l  e.,  the 
amount  by  which  the  eyes  can  diverge  in  a  vertical  plane,  is  de- 
ternnned  by  the  strength  of  prism  placed  base  up  or  down  before 
the  eyes,  which  the  latter  can  overcome  when  looking  at  a  dis- 
tant object.  The  right  snrsumvcrgejice  (in  which  the  prisms  are 
so  adjusted  as  to  cause  the  right  visual  line  to  be  the  higher  of  the 
two)  and  the  left  sursumvergence  should  both  be  ascertained. 
It  is  usually  best  to  leave  some  interval  of  time  between  the  two 
tests,  as  after  making  the  efifort  required  to  produce  right  sur- 
sumvergence (or  left  deorsumvergence)  it  is  difficult  at  once  to 
perform  the  contrary  action. 

A  difference  of  1°  or  more  between  the  right  anil  Ictt  sursum- 
vergence or,  in  any  case,  a  sursumvergence  exceeding *1°  (prism), 
indicates  the  probable  existence  of  a  hyperphoria. 


NEW  CLASSIFICATION  OF  MOTOll  ANOMALIES.  39 

Way  in  which  the  Tests  are  applied  in  Practice.  In  prac- 
tice I  have  found  it  best  to  apply  the  tests  in  the  following  order: 

(1)  Inspection,  I  note  the  apparent  relations  of  the  eyes  in 
the  primary  position  and  also  for  associated  parallel  and  con- 
vergent movements,  using  for  the  purpose  some  rather  fine  test- 
object  such  as  a  pen-point  which  the  patient  is  made  to  follow 
with  the  eyes  as  it  is  carried  in  different  directions.  Any  very  obvi- 
ous deflection,  e.  g.,  a  marked  concomitant  strabismus  or  a  par- 
alytic squint,  can  be  made  out  at  once  by  this  means  alone. 

(2)  Screen  and  Parallax  Tests.  These  are  made  simultan- 
eously. First,  a  test-object  20  feet  off  is  taken,  and  then  one  at 
the  ordinary  reading  distance.  If  inspection  has  revealed  any 
marked  deviation  or  one  which  increases  notably  in  any  given 
direction  of  the  gaze,  the  screen  test  also  is  applied  in  different 
portions  of  the  field  of  fixation  in  order  to  corroborate  these  find- 
ings. 

(3)  Equilibrium  Test  both  for  distance  and  near  with  the 
phorometer  or  with  prisms  in  the  trial-frame. 

(4)  Test  for  Divergettce  by  means  of  prisms  placed  base  in 
before  the  eyes  (Abducticn-test  of  most  authors). 

(5)  Determination  of  the  Convergence  Near-point  both  in 
the  median  line  (test  for  bilateral  convergence)  and  also,  as  has 
been  previously  explained  in  the  course  of  this  brochure,  in 
lateral  positions  of  the  gaze  (test  of  eccentric  convergence). 

(6)  Test  for  Convergence  by  prisms  placed  base  out  before 
the  eyes  (Adduction-test  of  most  authors). 

(7)  Diplopia  Test  with  candle  at  40"  or  more,  and  some- 
times also  with  card  and  dot  at  XT'.  In  order  to  make  this  test 
available  for  diagnosis  we  must  Have  some  ready  method  of  re- 
cording which  shall  indicate,  not  only  the  character  of  the  diplo- 
pia, but  also  its  approximate  amount,  the  point  at  which  it  be- 
gins to  appear,  and  the  way  in  which  it  increases  or  decreases  in 
different  directions  of  the  gaze.* 

These  comprise  all  the  tests  really  necessary,  and  all  these  can 
in  most  cases  be  readily  performed  within  ten  minutes.  If 
further  tests  are  thought  requisite,  the  Sursumvergence  Test  (8) 

*A  sample  of  the  scheme  which  I  have  adopted  for  my  entries  is 
as  follows: 

Eu  20",  Er  25^^— DL;  Eu  25^,  Er  30«-DL  2",  DX  2",  which  would 
mean  that  when  the  eyes  were  carried  25°,  to  the  right  and  20°  up 
from  the  primary  position  vertical  diplopia  appeared:  the  image 
of  the  left  eye  being  lower  (left  diplopia):  and  that  when  the  eyes 
were  carried  30°  to  the  right  and  25°  up  the  image  of  the  left  eye 
was  2°  below  and  2°  to  the  right  of  that  found  by  the  right  eye 
(i.  e.,  there  was  a  left  and  crossed  diplopia  of  2°  each). 


40  NEW  CLASSIFICATION  OF  MOTOR  ANOMALIES. 

and  the  mapping  out  of  the  Field  of  Fixation  (9),  may  be  under- 
taken. If  they  are,  they  should  be  left  to  the  last,  as  they  gener- 
ally cause  considerable  strain  of  the  eyes,  and  hence,  if  performed 
early,  are  apt  to  derange  the  normal  relations  of  the  eyes,  and 
thus  interfere  with  any  tests  that  may  be  made  afterwards. 

If  the  patient  is  ametropic  or  presbyopic,  the  various  tests  enu- 
merated should  be  made  both  with  and  without  the  correcting 
glasses,  in  order  to  ascertain  the  effect  of  the  latter  upon  the  mus- 
cular condition ;  and  other  factors  that  might  modify  the  latter, 
e.  g.,  the  existence  of  atropine  mydriasis,  should  also  be  noted. 

(To  be  continued.) 


Reprinted  from  Annals  op  Ophthalmology,  January,  1897. 


A  NEW  CLASSIFICATION  OF  THE  MOTOR  ANOMA- 
LIES OF  THE  EYE,  BASED  UPON  PHYSIO- 
LOGICAL PRINCIPLES. 

the  prize  essay  of  the  alumni  association  of  the  college  of 
physicians  and  surgeons,  new  york,  for  1896. 

By  Alexander  Duane,  M.  D., 

NEW  YORK. 

Part  2.    Pathology. 

IV..  Classification  of  Ocular  Deviations.  Nature  of  functions 
that  may  be  affected.— Nature  of  lesions  affecting  these  functions. 
— Hypokinesis,  Hyperkinesis,  Parakinesis.— Variation  in  degree 
of  the  lesions.  Superable  and  insuperable  deviations  (Hetero- 
phoria  and  Squint)  .—Classification  propounded.— Comitant  and 
non-comitant  deviations.— General  diagnostic  laws  based  upon 
the  presence  or  absence  of  comitancy.— Transformation  of  non- 
comitant  into  comitant  deviations. 

V.  Anomaliesoftlie  Individual  Muscles.  Muscular  under-action 
and  over-action.  Three  main  varieties.— Structural  muscular  de- 
viations. Structural  (Muscular)  squint  (Sclineller's  cases). 
Structural  heterophoria.— Insertional  squint  and  heterophoria.— 
Innervational  deviations.  Muscular  Paresis.  Muscular  Spasm; 
varieties  and  cases.— Symptoms  and  Differential  Diagnosis  of  the 
different  Varieties  of  Muscular  Over-action  and  Under-action. 
Identity  in  the  symptoms  presented  by  the  three  varieties.  Con- 
genital deviations.  Course  of  acquired  deviations.  Diagnosis 
between  under-action  and  over-action.  Slight  weakness  and 
over- action  (explaining  cases  of  heterophoria  and  particularly 
hyperphoria).  Diagnosis  by  the  double  images.  Principles  and 
diagnostic  tables.  Deductions  from  the  tables.  Treatment  of 
muscular  over-action  and  under-action.— Tremor  of  individual 
ocular  muscles;  Unilateral  nvstagmus. 

VI.  Anomalies  of  Associated  Parallel  Movements.  Hypokm- 
sis.  Paresis  and  insufficiency  of  associated  parallel  movements. 
Spasm  of  associated  i.arallel  movements.  Peculiar  case  of  spasm 
observed  by  the  autliov.— Parakinesis  of  assocuited  movements 
(Nystagmus).     Theory  of  nystagmus. 

VII.  Anomalies  of  Convergence.  Hypokinesis.  Paralysis  of  con- 
vergence.—Convergence-insufficiency.    Signs.    Nature  and  etiol- 


42  XEW  CLASSIFICATION  OF  MOTOR  ANOMALIES. 

ogy.  Varieties  of  non-accommodative  convergence-insufficiency. 
Accommodative  convergence-insufficiency;  varieties.  Course. 
Complications.  Symptoms.  Treatment. — Hyperkinesis.  Spasm 
of  convergence.  Convei'gence-excess.  Signs.  Etiology.  Va- 
rieties of  non-accommodative  and  of  accommodative  converg- 
ence-excess.    Course.     Complications.     Symptoms.     Treatment. 

VIII.  Anomalies  of  Divergence.  Hypokinesis. — Divergence-insuf- 
ticieucv.  Signs.  Etiology.  Idiopathic  and  secondary  diverg- 
ence-insiifticiency.  Differentiation  of  the  two  forms.  Course. 
Symptoms.  Treatment.  —  Hyperkinesis.  Divergence-excess. 
Signs.  p]liology.  Primary  and  secondary  divergence-excess. 
DiftVrciitiatioii  of  the  two.      Course.     Symptoms.     Treatment. 

IX.  Anomalies  of  Sursumvergence.  Hypokinesis.  Sumsurverg- 
encc-ins\ifficit'iicy.  —  Hyperkinesis.  Sursumvergence-excess. 
Sursunivergencc-liyperphoria  and  vertical  strabismus.  Peculiar 
cases;  anatr()i)ia  and  catatropia. 

X.  Anomalies  of  Rotation  Movements. 

XI.  Recapitulation.  Nature  of  Outward,  Inward  and  Vertical 
Deviations  (Exoiihoria.  Plsophoria  and  Hyperphoria).  Varieties 
of  each  and  their  dilferentiation. 

IV. 

THE  CLASSIFICATION  OF  OCULAR  DEVIATIONS. 

We  have  seen  in  Section  II.  of  this  brochure  that  as 
physiologists  we  have  to  consider  not  only  the  movements 
of  the  individual  muscles  and  the  relative  power  of  the 
latter,  but  also,  and  more  particularly,  the  associated  move- 
ments of  the  eyes  produced  by  the  coordinated  actions  of 
these  muscles.  It  seems  obvious  that  the  same  principles 
which  we  apply  to  the  physiology  of  the  ocular  movements 
should  also  be  applied  to  their  pathology,  and  that  in  classi- 
fying motor  disorders  of  the  eye  we  should  concern  our- 
selves not  simpj}!  icith  the  disorderi<  and  weaknesses  of  the 
Duisrhs  as  such,  hut  also  with  the  affections  of  all  the  various 
QHOvements  of  which  either  e//e  alone  or  both  et/es  together 
are  susceptible.  Reasoning  in  this  way,  we  shall  ask  if  we 
do  not  in  actual  practice  meet  with  pathological  conditions 
which  may  be  classified  into  the  following  groups,  corre- 
sponding to  the  physiological  groups  which  we  have  al- 
ready studied? 

(1)  Disorders  of  individual  muscles. 

(2)  Disorders  of  associated  parallel  movements. 

(3)  Disorders  of  convergence. 

(4)  Disorders  of  divergence. 

{5j   Disorders  of  sursumvergence. 

(6)   Disorders  of  the  rotation  (or  swivel)  movements. 


NEW  CLASSIFICATION  OF  MOTOR  ANOMALIES.  43 

I  think  that  we  have  a  sufficient  number  of  clinical  facts 
to  enable  us  to  give  an  affirmative  answer  to  this  query. 

For  example,  we  meet  with  quite  a  number  of  cases  in 
which  the  power  of  convergence  is  weak — a  state  that  we 
might  attribute  (as  indeed  it  often  is  attributed)  to  an  in- 
trinsic weakness  of  the  interni,  were  it  not  for  the  fact  that 
the  working  of  the  latter  in  associated  parallel  movements 
is  quite  normal.  Here  then,  evidently,  it  is  the  function  of 
convergence  that  is  at  fault  and  not  the  action  of  the  in- 
terni per  se.  Similarly  we  find  excessive  divergence  action 
which  can  not  be  attributed  to  weakness  of  the  interni, 
since  the  latter  act  normally  both  in  convergence  and  in 
lateral  movements,  nor  yet  to  excessive  strength  of  the  ex- 
terni  as  such,  since  the  latter  in  associated  parallel  move- 
ments do  not  carry  the  eye  too  far  outward.  In  this  case, 
therefore,  it  is  the  function  of  divergence,  and  not  the 
power  of  the  interni,  or  externi,  that  is  at  fault.  Both  this 
condition  and  the  preceding  one  exhibit  the  common  symp- 
tom of  divergence  in  fixation  and  would  hence  ordinarily 
be  classed  together  as  examples  of  exophoria;  but  in  classi- 
fying them  thus  we  should  be  naming  not  the  disease  but 
the  symptom.  The  symptom,  moreover,  while  the  most  ob- 
vious, is  not  necessarily  the  most  important  feature  of  the 
condition  in  question ;  and  in  our  therapeusis  we  aim  not 
so  much  to  abrogate  the  exophoria  per  se,  as  to  remove  the 
state  (defective  convergence,  excessive  divergence)  caus- 
ing the  exophoria. 

Similar  instances  might  be  given  of  other  varieties  of 
motor  disorders  in  which  also  the  function  involved  is  an 
ocular  movement  and  not  an  ocular  inuftcle.  The  considera- 
tion of  these,  however,  will  be  deferred  until  later  when 
they  can  be  discussed  more  in  detail ;  those  given  above 
being  regarded  as  sufficient  for  purposes  of  illustration. 

If,  then,  any  one  of  the  ocular  motor  functions  may  be 
involved  independently  of  the  rest,  we  must  next  inquire 
what  may  be  the  nature  of  the  lesion  affecting  it.  In  ans- 
wer to  this  it  may  be  said  that  any  motor  function  may  be 
deranged  in  either  one  of  three  ways. 

(1)  It  may  be  performed  inadequately  or  not  at  all — de- 
ficiency of  moyement  ( II//2>ol-i)ie.sis). 


44  NEW  CLASSIFICATION  OF  MOTOR  ANOMALIES. 

(2)  It  may  be  performed  excessively — excessive  move- 
ment (  JIi/perK'inesis). 

(3)  It  may  be  performed  irregularly  or  in  successive 
phases  of  excess  and  inadequacy — irregular  movement 
(  Parakinesis). 

To  the  question  whether  disorders  having  these  various 
characters  are  actually  encountered  in  connection  with  the 
ocular  movements,  clinical  facts  once  more  enable  us  to 
give  an  affirmative  answer.  It  must,  however,  be  under- 
stood that  these  conditions,  namely  hypokinesis,  hyper- 
kinesis  and  parakinesis,  may  be  present  in  very  varying 
degrees.  Thus  weakness  (hypokinesis)  may  vary  all  the 
way  from  a  slight  and  transient  enfeeblement  to  a  complete 
paralysis;  and,  similarly,  excessive  action  (hyperkinesis) 
may  range  from  a  moderate  degree  of  over-action  to  an 
intense  and  permanent  spasm.  It  thus  happens  that  there 
are  some  deviations  so  slight  as  to  be  habitually  corrected 
by  the  supplementary  ^ffort  that  the  patient  is  able  to  ex- 
ert ( Supe fable  deviation, Latent  st)'ahis')nus,IIeteropJioria  ); 
while  there  are  other  deviations  so  great  that  the  patient 
can  overcome  them  with  difficulty  if  at  all,  and  which  are 
hence  more  or  less  constantly  present  (  Insuperable  devia- 
tion. Manifest  squint,  Ileterotropia ).  These  latter  again 
are  divided  according  to  the  constancy  of  their  occurrence 
into  Interniitte]it,  when  present  at  intervals,  Periodic,  when 
recurring  regularly  under  certain  conditions  {e.  g.  in  con- 
vergence), and  (Jonsta)it.  It  should  be  borne  in  mind, 
however,  that  these  distinctions  all  represent  differences 
simply  of  degree  and  not  of  kind. 

The  foregoing  considerations,  confirmed  and  modified  by 
the  results  of  the  examination  of  quite  a  large  amount  of 
clinical  material,  have  led  me  to  propound  the  following 
classification  of  the  motor  anomalies  of  the  eye. 

CLASSIFICATION    OF    THE    MOTOR    ANOMALIKS    OF    TIIK 
EYE.     OCULAR  DEVIATIONS  IN  (JENERAL  DUE  To 

L     Anomalie.s  of  Iiulividual  IMusclcs  oi-  of  tlicir  Nfivc-iiucU'i. 
{a)    Jhider-actioti.     The  iiiusclf  works  iiiclliciciitly. 
L  Hecause  tiic  niusrit'  itsi'If  is  ill-di'volopi'd  or  atropliii-d  (Struc- 
tural S(|uint),  or  because  its  attachnieuts  are  unfavorable  for 

cfTcctive  action  (  Iiiscrtioual   Scuiiiit). 


NEW  CLASSIFICATION  OF  MOTOR  ANOMALIES.  45 

2.  Because  of  iinpairinent  of  the  nerve  or  nerve-iiueleus  supply- 
ing the  niusele  (Paretic  S<iuint). 
(h.)   Orer-action.     Tlie  nuisch-  works  excessively. 

1.  Because  the  muscle  itself  is  over-developed  (Structural  Squint) , 

or  because  its  attachments  are  favorable  for  effective  action 
(Insertional  Squint). 

2,  Because  of  over-excitation  of  the  nerve  or  nerve-nucleus  sup- 

plying the  muscle  (Spastic  Squint), 
(c.)  Perrerted  action.     Clonic  spasm  of    individual  nniscles    (some 
rare  forms  of  Nystagnuis) . 

II.  Anomalies  of  the  Association  Centres  for  Parallel  Movements. 
{a.)  Under-action.  Producing  an  equal  impairment  in  the  move- 
ment of  both  eyes  either  (1)  up,  (2)  down,  (3)  to  the  right, 
(4)  to  the  left,  or  (5)  obliquely,  or  (6)  an  equal  impairment 
of  the  rotary  (swivel)  movements  of  the  two  eyes.  (Associ- 
ated Paralysis,  Conjugate  Paralytic  Deviation.) 

{b.)  Orer-action.  Producing  an  equal  excessive  movement  of  both 
eyes  in  the  same  direction  (Associated  Spasm,  Conjugate 
Spastic  Deviation) . 

(c.)  Perverted  action.  Clonic  Spasm  (Ordinary  Nystagmus;  includ- 
ing Lateral,  Vertical,  Rotary  and  Mixed  Nystagmus). 

III.  Anomalies  of  the  Centre  for  Convergence-Movements. 

(rt.)  Under-action.  Convergence-Insutftbiency  (producing  one  va- 
riety of  Comitant  Divergent  Squint  or  Exophoria) . 

1.  Accommodative  (due  to  relaxed  accommodation  in  myopes). 

2.  Non-accommodative. 

{h.)  Orer-action.  Convergence-Excess  (producing  one  form  of 
Comitant  Divergent  Strabismus  or  Esophoria). 

1.  Accommodative  (due  to  excess  of  accommodation  in  hyperme- 

tropes.) 

2.  Non-accommodative. 

IV.  Anomalies  of  the  Centre  for  Divergence  Movements. 

{a.)  Under-action.  Divergence-Insuificieney  (producing  one  form 
of  Comitant  Convergent  Squint  or  Esophoria). 

{b.)  Orer-action.  Divergence  excess  (producing  one  form  of  Com- 
itant Divergent  Squint  or  Exophoria) . 

V.  Anomalies  of  Sursumvergence. 

(«.)     Under-action.     Sursumvergence-Insufficiency. 

(b.)  Over-action.  Sursumvergence-Excess  (producing  constant  or 
intermittent  vertical  divergence  of  the  visual  lines:  includ- 
ing cases  in  which  one  visual  line  is  habitually  above  (Spas- 
tic Right  or  Left  Hyperphoria),  and  cases  in  which  some- 
times one,  sometimes  the  other,  rises  higher  (Alternating 
Hyperphoria) . 

VI.  Anomalies  of  Rotation  (Swivel  or  Torsion)  Movements. 

(rt.)  Habitual  or  intermittent  divergence  of  the  Vertical  meridians 

(Cyclophoria  Divergens). 
{b.)  Convergence  of  the  vertical  meridians  (Cyclophoria  Couverg- 

ens) . 


46  NEW  CLASSIFICATION  OF  MOTOR  ANOMALIES. 

VII.  Mixed  Forms.     Many  varieties  iiiehidinfi:  particularly — 

(a.)   ('(mverffeiice-Iusuffieieiu'y  combined  with  Diverg'ence-Excess. 

(h.)  Convergfence-Iiisiiilicieiicy  comhiiicd  with  Diverfj^ence-Insuffi- 
ciency. 

(c.)  Coiivertji'iice-lnsutticiency,  simple  or  complicated,  combined 
with  under-actioii  or  over-action  of  one  or  more  of  the  lat- 
eral or  vertical  muscles. 

(d.)  Convergence-Excess  combined  with  Divergence-Insufficiency. 

(c.)  Convergence-Excess  combined  with  Divergence-Excess. 

(/.)  Convergence-Excess,  simple  or  complicated,  combined  with 
under-action  or  over- action  of  one  or  more  of  the  lateral  or 
vertical  muscles. 

{g.)  Under-action  of  one  nuiscle  combined  with  over-action  of 
another. 

Before  taking  up  the  study  of  the  individual  anomalies, 
it  is  well  to  consider  one  or  two  features  common  to  all  of 
them. 

Comitant*  and  Non=comitant  Deviations.  A  wide  differ- 
ence exists  both  as  regards  symptoms  and  physical  signs 
between  motor  disorders  in  which  the  amount  of  deviation 
constantly  changes  according  to  the  direction  of  the  gaze 
( Non-coinitant  deviations)  and  those  in  which  it  remains 
the  same  (  Coniifant  deviations).  The  former  is  apt  to  be 
much  the  more  troublesome  of  the  two  to  the  patient,  par- 
ticularly when  the  deviation  keeps  changing  while  the  eyes 
are  executing  associated  parallel  movements.  This  is  ap- 
parently due  to  the  fact  that  the  symptoms  occasioned  by 
the  deviation,  changing  as  they  do  with  every  alteration  in 
the  position  of  the  eyes,  cannot  be  allowed  for  nor  be  as 
readily  ignored  as  when  they  are  constant. 

That  is,  since  the  patient  sometimes  sees  single,  sometinu^s  doul)le, 
i.  e.  is  affected  with  an  error  of  varying  amount,  he  cannot  as  readily 
make  allowances  for  his  peculiar  state  of  vision  as  if  he  saw  double 
all  the  time  and  had  a  constant  error  to  contend  with.  Moreover,  it 
is  less  easy  for  the  eye  to  suppress  a  false  inuige  when  the  latter,  in- 
stead of  occupying  always  the  same  .spot  upon  the  retina,  as  it  does 
in  comitant  deviations,  occupies  a  nund)er  of  different  spots  in  suc- 
cessif)n,  as  it  does  in  the  case  of  a  non-comitant  deviation.  Hence 
the  diplopia  tends  to  persi.st  much  longer  in  non-comitant  disorders 
than  in  those  that  are  comitant.  Besides,  the  very  fact  that  the  de- 
flection is  changeable  in  amount  is  the  cause  of  the  most  trying  syinp- 
toms  (false  projection  and  vertigo)  of  a  non-comitant  deviation;  and 

•Tlic  word  "comitant"  is  lure-  i-niiiloytd  in  preference  to  tlif  more  usual  "ecu 
comitant  "  as  lieinn  botli  l)riifir  and  ctynioloKically  better. 


NEW  CLASSIFICATION  OF  MOTOR  ANOMALIES.  47 

when  the  deflection  becomes  constant  in  (juantity  for  all  directions  of 
the  gaze,  these  symptoms  are  apt  to  disappear. 

It  is  obvious  that  an  (ifftction  of  the  individtad  ucular  iiiia^clcs. 
whether  in  the  direction  of  excess  or  of  deficiency,  must  cause  a 
non-comitant  deviation,  the  angle  between  the  two  visual  lines  be- 
coming greater  and  greater  the  more  the  eyes  are  carried  in  the 
direction  in  which  the  muscles  in  question  normally  exert  their  great- 
est influence.  Thus  in  a  paralysis  of  the  right  externus  the  right  eye 
will  lag  more  and  more  behind  its  fellow  in  proportion  as  the  eyes 
are  carried  to  the  right;  and  in  paralysis  of  the  right  superior  rectus 
the  right  eye  will  fall  more  and  more  below  the  level  of  the  other, 
the  more  the  attempt  is  made  to  direct  the  gaze  up  and  to  the  right. 
In  fact,  it  is  by  this  very  changeableness  or  non-comitancy  of  the 
deviation  that  we  make  our  diagnosis  of  the  existence  of  muscular 
paralysis  or  spasm. 

On  the  other  hand,  a  deviation  due  simph^  to  an  over-action  or 
under-action  of  either  dirercjencc  or  convergence  will  not  change  in  the 
performance  of  associated  lateral  or  vertical*  movements,  as  long  as 
the  object  of  fixation  does  not  appreciably  approach  or  recede  from 
the  eyes.  For,  for  any  given  distance,  the  amount  of  convergent  or 
of  divergent  action  will  be  constant  and  the  excess  or  deficiency  of 
this  action  will  also  be  constant,  no  matter  whether  the  eyes  are  look- 
ing straight  ahead,  or  laterally,  or  up  or  down.  If,  however,  the  dis- 
tance of  the  object  of  fixation  from  the  eye  is  altered,  the  amount  of 
convergent  or  divergent  action  changes  also,  and  in  general  the 
amount  of  deflection  will  change  as  well.  Thus  in  a  pure  conver- 
gence-insufficiency the  deviation  will  become  more  and  more  appar- 
ent as  the  limit  of  convergence  is  approached  and  will  disappear  alto- 
gether when  the  convergence  is  relaxed,  i.  e.  when  the  patient  is 
looking  at  a  distance.  In  the  case  of  a  divergence-insufiiciency  the 
reverse  will  hold  good. 

In  anomalies  of  associated  parallel  movements  the  motions  of  the  eyes 
are  strictly  comitant,  and  in  fact  the  visual  lines  remain  everj-where 
parallel,  since  the  ocular  movements,  while  either  restricted  or  in  ex- 
cess in  some  given  direction,  are  restricted  or  in  excess  to  the  same 
degree  in  both  eyes.  For  example,  in  a  case  of  restricted  sursum- 
version  both  eyes  will  fail  to  move  up,  but  as  the  failure  affects  both 
to  an  equal  degree,  the  visual  lines  will  in  the  performance  of  this 
movement  remain  parallel  up  to  the  point  where  they  cease  to  move 
at  all. 

The  foregoing  facts  may  be  recapitulated  as  follows : 
(1)  A  deviation  which  increases  or  decreases  in  the  per- 
formance of  associated  paraUel  movements  hy  the  eyes  signi- 
Jies  an  anomali/  of  one  or  more  of  the  ocular  muscles  —  the 

♦This  statement  is  not  absolutely  accurate,  for,  owing  to  the  fact  that  the  visual 
lines  tend  to  diverge  when  the  gaze  is  directed  upward  and  to  converge  when  they 
are  directed  downward,  an  exophoria  otherwise  comitant  will  show  an  increase  in 
the  upper  and  a  decrease  in  the  lower  portions  of  the  field  of  fixation. 


48  NEW  CLASSIFICATION  OF  MOTOR  ANOMALIES. 

direction  in  which  it  increases  corresponding  to  that  in 
which  the  action  of  the  muscles  affected  is  normally  most 
pronounced. 

(2)  ^1  dtrii(ti())i  irjiirlt  rotiai iiK.coustant  or  nearl//  soir/dle 
the  eijes  are  perform uui  paraUel  movements  i,s  due,  not  to  an 
anomah/ of  indh'idual  muscles,  bat  to  an  anomaly  of  some 
one  of  the  associated  movements  of  the  eyes. 

(3)  A  deviation  lohich  increases  as  the  eyes  are  converged 
denotes  a  convergence-anomaly,  and  one  ivhich  increases  as 
the  eyes  are  passing  from  co))rerrience  to  i)ara]lelisnt  a  diver- 
gence-anomaly. 

Transformation  of  Non=comitant  into  Comitant  Devia= 
tions.  Non-comitancy  in  parallel  movements  might  be 
remedied  by  restricting  or  increasing  the  action  of  the  un- 
affected eye  in  the  same  sense  as  that  in  which  the  action 
of  the  affected  eye  is  restricted  or  increased;  /.  e.  by  con- 
verting the  anomaly  from  one  of  Class  I.  into  one  of 
Class  II. 

This  is  done  in  actual  practice  when,  c.  f).  in  a  paralysis  of  the  su- 
perior oblique  of  the  right  eye  we  teuotoniize  its  associated  antaj?on- 
ist,  the  inferior  rectus  of  the  other  eye,  thereby  weakening  the  lat- 
ter artificially  in  precisely  the  same  sense  and  to  the  same  extent 
that  the  right  eye  is  weakened  naturally.  In  nature  a  similar,  though 
less  perfect,  result  is  commonly  attained  l>y  the  deA'elopment  of  a 
spasm  of  the  direct  antagonist  or  of  a  pair  of  antagonistic  muscles  in 
the  eye  ai¥ected.  Thus  in  a  paralysis  of  the  right  externus,  wliich 
produces  a  deviation  confined  to  the  right-  half  of  the  field  of  fixation, 
is  usually  followed  after  a  time  by  a  spastic  contraction  of  the  right 
internus,  which  produces  a  deviation  of  the  same  character  in  the 
left  half  of  the  field  of  fixation.  Thus  the  affected  eye  gets' to  squint 
inward,  not  only  when  looking  to  the  right,  but  also  when  looking  to 
the  left,  and  the  deviaticm,  from  being  markedly  non-comitant,  be- 
comes comitant  or  nearly  so.  A  similar  occurrence  is  regularly  ob- 
served in  paralysis  of  the  other  nuisdes. 

A  similar  tendency  to  replace  non-comitant  by  comitant  deviations 
appears  to  prevail,  although  possil)ly  1<>  a  less  extent,  in  divergence 
and  convergence  anomalies.  Thus  a  convergence-insufficiency,  exist- 
ing at  first  without  any  complication,  is  very  apt  later  on  to  become 
associated  with  a  divergence-excess,  so  that  a  sensibly  constant  devia- 
tion outward(exoi»horia)is  present  both  for  far  and  near.where  origin- 
ally it  was  i)resent  for  lu-ar  only.  So  also  a  convergence-excess  may 
lead  to  a  divergence-insufiiciency,  so  that  the  I'sophoria  which  at  first 
was  marked  only  for  lu/ar  now  becomes  etjually  pronounced  for  dis- 
tance.    Tliis  compensatory  process,  by  which  comitancy  is  evolved 


NEW  CLASSIFICATION  OF  MOTOR  ANOMALIES.  49 

<nit  of  a  iion-coiuitant  state,  is  doubtless  the  ivason  for  the  many 
iuixe<l  forms  of  divergence  and  convergence  anomalies  that  we  meet 
with;  and  the  process  itself  may  actually  be  watched  in  following 
the  develoj^meiit  of  many  cases  of  squint. 

The  process  in  fact  seems  to  take  place  so  generally  that 
it  seems  safe  to  enunciate  the  following  law: 

.1  iioii-ronrifant  deviation  u.sualft/  feuds  to  become  comi- 
frnit,  there  heing  superadded  to  the  morbid  condition  already 
existing  another  Inj  means  of  ichich  the  former  is  generalized 
and  rendered  sensibly  equal  throughout  the  whole  Jield  of 
fixation. 


V. 

ANOMALIES  OF  THE    INDIVIDUAL  MUSCLES.* 

liypokineses  and  Hyperkineses  ( Paretic  and  Spastic 
Squint),  Over-action  or  under-action  of  the  individual 
ocular  muscles,  giving  rise  to  a  disturbance  of  the  normal 
balance  of  the  eyes,  may  be  due  to 

(a)  Over  or  under  -  development  of  the  muscle  itself 
(structural  squint,  structural  heterophoria). 

(b)  Variations  in  the  origin,  insertion  and  direction  of 
the  muscles  and  in  the  length  of  their  tendons  (insertional 
squint  or  heterophoria) . 

(c)  Over  or  under-excitation  of  the  muscle  due  to  some 
affection  of  its  nerve  or  nerve-nucleus  (paretic  and  spastic 
squint  and  heterophoria) . 

The  hypertrophy  or  the  non-development  of  the  muscles, 
producing  what  I  have  called  structural  deviation  is  prob- 
ably in  many  cases  congenital.  This  is  certainly  so  in  those' 
cases  of  defective  elevation  of  the  eye  (frequently  asso- 
ciated with  ptosis)  which  have  been  proved  by  dissection 
to  be  due  to  absence  of  the  superior  rectus  (Fuchs).  I 
have  seen  one  marked  instance  of  this  congenital  anomaly 
in  which  ptosis  co-existed  with  almost  entire  absence  of 
elevation,  and  I  am  inclined  to  think  that  several  other 
cases  of  less  complete  paralysis  of  elevation,  which  I  have 


♦This  section,  since  its  first  presentation  to  the  Prize  Committee,  has  been  largelv,- 
added  to  and  to  a  certain  extent  re-modeled. 


-50  NEW  CLASSIFICATION  OF  MOTOR  ANOMALIES. 

observed,  were  likewise  congenital  and  structural  in  origin.* 

Another  class  of  cases  of  structural  deviation,  of  quite 
frequent  occurrence,  are  those  which  Schneller  (Arch,  fiir 
Ophth.  xxiii.  No.  3)  describes  under  the  name  of  itniscnlar 
sfrabi.'imiis.  Such,  for  example,  are  those  cases  of  diver- 
gent strabismus  in  which,  at  the  time  of  operation,  we  find 
the  external  rectus  thick,  broad  and  fleshy,  and  provided 
with  a  dense,  broad  tendon,  while  the  internal  rectus,  on 
the  contrary,  is  thin  and  has  a  narrow  tendon,  often  split  up 
into  separate  fibrils.  Schneller  in  these  cases  found  that 
the  tendon  of  the  externus,  instead  of  being  about  equal  to 
that  of  the  internust,  was  from  one-fourth  to  one-third 
greater.  In  convergent  strabismus,  on  the  other  hand,  the 
ratio  was  reversed,  the  tendon  of  the  externus  being  much 
thinner  than  that  of  the  internus  and  the  externus  itself 
being  comparatively  meager  and  undeveloped, 

Schneller  reports  thirty-four  cases  of  such  muscular 
(structural)  strabismus.  He  regards  them  (probably  with 
justice)  as  congenital  in  origin. 

Otliers  have  supposed  that  these  were  cases  of  acciuired  atrophy 
(atrophy  of  disuse).  But  the  patlioloj^ical  ehang'es  are  those  of  sim- 
ple non-devek)pnieiit  rather  than  atrophy,  the  inuseuhir  fibres  being 
merely  insutheient  in  number  or  size  and  showings:  no  e>idenees  of 
fatty  or  filn-ous  transformation  nor  of  myositis. 

The  diagnostic  features  of  a  muscular  squint,  according 
to  Schneller,  are 

(1)  The  deviation  is  not  relieved  by  atropinization  and 
correction  of  the  refraction  (distinction  from  accommoda- 
tive convergence-excess  and  convergence-insufficiency). 

(2)  The  field  of  fixation  (/.  e.  the  range  of  excursion  of 
the  eyes)  is  abnormally  large  in  one  direction  and  abnor- 
mally limited  in  the  opposite.  If  the  sum  of  the  inward 
excursions  of  the  two  eyes  exceeds  the  sum  of  the  outward 
excursions  by  30'\  a  convergent  strabismus  is  produced ; 
while  a  preponderance  of  outward  excursions  over  inward 
excursions  of  12'  is  sufficient  to  cause  a  divergent  squint 
(Schneller). 

*Scc  article  by  tlK- autliur  1)11  •■  I'aialysis  of  tlic  SiiiHii.>r  Kutu-^  aiul  Us  HcnriiiK 
upon  tilt  Theory  of  Mustular  Iiisufricicncy  "  (Archives  ol  t)i)lit!ialiiiolu),'y.  vol.  xxiii.. 
No.  1,18M.) 

tSchnellcr  fotiud  the  normal  ratio  between  the  breadth  of  the  externu.s-tendoii 
and  the  internu.s-tendoii  to  be  102:100.  His  measiircnients  were  made  so  as  to  include 
more  uf  the  .-scleral  attachments  than  in  those  made  by  other  observers  who  have 
found  the  ratio  to  be  SS  ( Volkiiiaiiu)  ami  S<(  ( [•"uclis) 


NEW  CLASSIFICATION  OF  MOTOR  ANOMALIES.  51 

This  latter  statement  involves  a  fallacy,  strictly  speaking?,  if  the 
range  of  excursion  is,  as  is  usually  the  case,  determined  by  making 
the  eyes  follow  a  test-object  situated  within  a  foot  or  so  of  the  eye. 
For  in  this  case  when  the  eyes  are  directed  to  the  right,  the  amount 
of  excursion  outward  of  the  right  eye  =  the  absolute  amount  by  which 
the  externus  can  turn  it  outward  (abduction)  less  the  amount  by 
which  it  is  turned  inward  in  order  to  converge  upon  the  object  (con- 
vergence). The  latter  (convergence)  movement  will  be  exce^ssive 
either  if  the  right  iiitei'nus  acts  too  forcibly  in  response  to  an  ordi- 
nary impulse  of  convergence  (muscular  excess)  or  if,  the  muscle 
being  normal,  the  impulse  itself  is  excessive  (convergence-excess). 
In  either  case  the  net  movement  outward  will  be  limited,  even  when 
the  actual  amount  of  abduction  produced  by  the  externus  is  normal. 
If,  then,  the  case  were  one  of  simple  convergence-excess  the  limita- 
tion of  outward  movement  would  be  the  same  for  both  ej'es, 
(.  e.,  the  same  whether  the  gaze  is  directed  to  the  right  or  to  the 
left;  but  if  it  were  one  of  muscular  squint,  i.  e.  of  actual 
insufficiency  of  the  externi  (or  preponderance  of  the  interni) 
the  limitation  might  be  either  unilateral  or  bilateral.  In  the  latter 
event  the  diagnosis  of  a  muscular  anomalj',  as  distinguished  from  a 
pure  anomaly  of  convergence,  would  be  substantiated  if  the  limita- 
tion of  abduction  were  found  to  be  the  same  for  all  distances,  far  as 
well  as  near. 

Degrees  of  weakness  or  of  over-development,  too  slight 
to  produce  actual  squint,  probably  form  an  important  ele- 
ment in  the  causation  of  many  cases  of  heterophoria  (".s'/r^^r- 
fura/  heteropJioria. ) 

Insertional  squint  or  heterophoria,  /.  e.  that  sort  of  mus- 
cular under-action  or  over-action  due  to  variations  in  the 
origin  and  insertion  of  the  tendons,  is  difficult  to  distin- 
guish from  the  structural  deviations  due  to  under  or  over- 
development of  the  muscular  fibre  itself.  The  structural 
deviations,  however,  are  frequently  congenital,  while  inser- 
tional squint  is  generally  acquired.  For  example,  a  very 
important  class  of  cases  coming  under  the  latter  category 
are  those  in  which  the  insertion  of  a  tendon  has  been  dis- 
placed by  a  tenotomij  or  an  advanremenf .  Here  by  the  op- 
eration an  insertional  anomaly  is  produced;  and  the  weak- 
ness or  over-action  resulting  from  this  artificial  anomaly  is 
precisely  similar  in  symptoms  and  objective  signs  to  weak- 
ness or  over-action  due  to  natural  causes  (paresis  or 
spasm,  for  example).* 

*Of  the  exactness  of  this  similarity  I  have  been  able  to  convince  myself  by  re- 
peated examinations  upon  cases  in  which  extensive  operations  had  been  made  either 
upon  the  lateral  or  vertical  muscles. 


52  NEW  CLASSIFICATION  OF  MOTOR  ANOMALIES. 

Another  class  of  cases  in  which  there  is  an  acquired  in- 
sertional  anomaly  are  those  in  which  a  direrr/enf  sfrahis- 
mus  /ia.s  (Jrveloj^ed  as  a  rcsti/f  of  tlie  (jradual  dit-erffence  of 
the  ovhits  taking  place  during  the  period  of  growth  in  child- 
hood and  youth.  This  divergence,  by  altering  the  angle 
of  insertion  of  the  tendons  and  the  amount  of  tendon  in 
contact  with  the  eye -ball,  increases  very  greatly  the  power 
of  the  externus  and  diminishes  that  of  the  internus,  and  in 
itself  is  quite  sufficient  to  account  for  the  development  of 
the  strabismus  (see  L.  Weiss,  Arch.  f.  Augenh.  xxix.  and 
Arch,  of  Oph.  xxv.  No.  3,  1896) .  The  anomaly  in  this  case 
is  of  great  importance  in  that  it  exaggerates  and  renders 
uncertain  the  effect  of  a  tenotomy  of  the  interni  when  made 
upon  children.  Admitting  Weiss' s  explanation  of  it,  the 
obvious  deduction  would  be  that  tenotomy  of  the  interni 
should  be  avoided  in  children  with  convergent  squint  who 
have  the  orbits  and  eyes  set  very  close  together,  since  in 
these  divergence  of  the  orbits  is  likely  to  take  place  subse- 
quently resulting  in  a  preponderance  of  the  externi,  which 
will  by  itself  suffice  to  correct  the  convergence. 

Other  kinds  of  insertional  anomalies  exist,  some  so  slight 
as  to  produce  only  a  moderate  degree  of  heteropliona,  in- 
stead of  a  squint.  They  often  develop  when  a  non-comi- 
tant  deviation  has  lasted  for  some  time,  and  help  to  trans- 
form the  latter  into  a  deviation  of  the  comitant  variety. 

Muscular  paresis  and  spasms (Innervational  Deviations). 
The  subject  of  the  paralyses  of  the  eye  muscles  has  been 
so  thoroughly  worked  out  and  so  ably  presented  by  the  two 
Graefes  and  Mauthner,  that  there  is  but  little  to  add  to  their 
statement.  The  few  points  to  which  it  seems  necessary  to 
call  attention  will  be  touched  upon  in  the  remarks  on 
diagnosis. 

Spasm  of  the  individual  ocular  muscles  may  occur 

(1)  As  an  cridviicc  <if  a  secotiddri/  deviation  in  a  soaiid 
ri/e  when  the  other  eye,  being  paretic,  is  yet  used  for  fixa- 
tion. 

Thus  sup).()Sf  thai  a  i)ati('iit  with  a  paresis  of  the  ri^^ht  fXtcnms 
ncvcrthch'ss  fixes  with  the  ri>,'-ht   eye  l)ecause  he  sees  Itetter  with  it. 


NEW  CLASSIFICATION  OF  MOTOR  ANOMALIES.  53 

Then  when  he  looks  at  some  object  situated  on  his  right  he  has  to 
exert  an  excessive  amount  of  force  to  turn  his  tixing  eye  out  suffi- 
ciently. The  same  amount  of  force  is,  by  the  law  of  association, 
also  transmitted  to  the  left  internus,  and  the  latter,  not  being  paretic, 
Avill  respond  with  normal  vigor  to  the  excessive  stimulus,  so  as  to 
carry  the  left  eye  nnich  further  to  the  right  than  its  fellow,  and 
hence  quite  to  the  right  of  the  object  of  fixation.  In  this  case,  as 
the  right  eye  follows  the  object,  and  the  left  eye  by  an  apparently 
excessive  action  shoots  past  it,  we  might  regard  the  condition  as  one 
of  veritable  spasm  of  the  left  internus ;  whereas  the  real  state  of  the 
case  is  that  the  latter  muscle  is  normal  and  contracts  excessively  only 
because  the  stimulation  that  it  receives  is  excessive.  These  cases  are 
therefore  correctly  denominated  as  cases  of  false  or  apparent  spasm. 

(2)  In  the  case  of  a  paralysis  of  an  ocular  musle,  a  spas- 
tic contraction  of  one  or  more  of  the  other  inuscks  in  the 
same  ei/e  takes  place,  by  virtue  of  which,  as  has  been  al- 
ready stated,  the  deviation  becomes  more  or  less  concomi- 
tant and  generalized  throughout  the  whole  field  of  fixation. 
This  contraction  finally  results  in  a  permanent  shortening 
(contracture)  of  the  muscles  affected,  but  before  this  stage 
has  been  reached,  a  temporary  and  varying  spasm  may  be 
set  up  in  the  antagonists  of  the  paralyzed  muscle,  so  as  to 
carry  the  deviation  and  the  diplopia  far  outside  of  the  field 
of  action  of  the  latter.  This  was  clearly  shown  in  the  fol- 
lowing case  which  came  under  my  care : 

Paralysis  of  Inferior  Rectus.  Varying  Spasm  of  Superior  Rectus 
of  same  eye.  H.,  male,  aged  29.  Vertigo,  blurring  of  sight,  and 
diplopia  for  past  two  years.  No  history  of  syphilis.  Presents  all  the 
evidences  (by  inspection,  screen,  and  diplopia  tests)  of  a  well-marked 
paresis  of  the  R.  inferior  rectus.  Vertical  diplopia  (with  image  of 
right  eye  below  =  DR)  increasing  to  6°  to  7°  (=14"  prism)  as  the 
eyes  are  carried  down  and  to  the  right;  diminishing  to  zero  when  the 
gaze  was  directed  down  and  to  the  left.  Moderate  crossed  diplopia 
everywhere;  increasing  when  eyes  are  directed  down  and  to  left. 
Vertical  diplopia  of  the  same  character  as  that  found  in  the  lower 
field  prevailed,  although  to  a  less  extent  in  the  upper  field;  most 
marked  in  looking  up  and  to  the  right  (Eu  &  r,  DR  increasing) .  This 
diplopia  in  the  upper  field  varying  much,  and  partially  superable  by 
voluntary  effort. 

Here  there  was  evidently  a  spasm  (variable  in  amount)  of  the  right 
elevators,  and  particularly  of  the  right  superior  rectus  (shown  by  the 
fact  of  the  vertical  diplopia  increasing  upward  and  to  the  rifjhf). 
The  vertical  diplopia  in  the  upper  part  of  the  field  might,  it  is  true, 
have  been  due  to  a  paresis  of  the  elevators  of  the  left  eye;  but  the 


54  NEW  CLASSIFICATION  OF  MOTOR  ANOMALIES. 

variable  character  of  the  diplopia  and  the  fact  that  it  was  siiperable 
by  voluntary  effort  negative  this  supposition. 

(3)  Spasm  (usually  slight)  of  one  or  more  of  the  ocular 
muscles  may  occur  as  the  result  of  h-riiotlri^  hsloiis  at  the 
base  of  tJie  hrain,  particularly  meningitis. 

(4)  Slight  transient  spasm  may  occur  in  chorea. 

(5)  Convulsive  tonic  spasm  may  occur  in  epilepsi/  and  Itifs- 
fen'a,  although  in  these  diseases  it  is  not  generally  the 
individual  muscles  that  are  affected,  but  the  associated 
movements  of  the  eyes  (particularly  the  parallel  move- 
ments and  movements  of  convergence).  Gowers,  however 
(Diseases  of  the  Nervous  System),  calls  attention  to  a  sort 
of  convulsive  seizure  that  maybe  styled  epileptoid,  in  which 
there  are  suddenly  developing  tonic  and  clonic  spasms  of 
one  or  more  ocular  muscles,  associated  with  more  or  less 
obtunding  of  the  consciousness. 

(6)  Finally  we  may  have  cases  of  non-pa roxiismal  and 
chronic  spai^ni  of  some  one  ocular  nmsclv,  which  causes  the 
eye  to  make  an  excessive  movement  as  soon  as  it  is  turned 
so  that  the  affected  muscle  can  act  upon  it.  Thus  cases 
have  been  described  in  which  a  spasm  of  the  external  rec- 
tus caused  the  eye  to  shoot  far  outward  as  soon  as  the  eye 
was  turned  past  the  middle  line.  Mauthner  (Augenmus- 
kelliihmungen)  casts  doubt  on  all  such  cases,  regarding 
them  as  probably  instances  of  secondary  deviation  of  a 
sound  eye  due  to  the  fact  that  the  other  eye  is  paretic  but 
still  performs  fixation,  so  that  an  excessive  impulse  is 
transmitted  to  both  eyes.  That  is,  he  would  class  all  such 
cases  under  the  category  of  false  or  apparent  spasm  (Group 
1  mentioned  above) .  But  this  statement  is  certainly  too 
sweeping,  since  cases  of  chronic  spasm,  although  doubtless 
rare,  do  occur,  as  witness  the  following  that  I  observed: 

Paralysis  of  L.  Externus;  Spasm  of  L.  Inferior  Oblique.  Ber- 
tha S.,  a{?ed  8.  Deviation  of  eyes  noticed  since  birth.  Used  to  h<»kl 
head  to  right  and  does  so  still  wlien  looking  intently  at  anything. 
L.  eye  eannot  move  out  beyond  median  line.  Wlien  eyes  are  car- 
ried horizontally  to  the  right,  L.  eye  siiddenlif  Jiies  itpward  and  he- 
cowes  buried  beneath  the  upper  fid.  In  associated  movements  in  lower 
field,  L.  eye  moves  normally  with  the  \i.  Behind  screen  L.  eye  de- 
viates high  up  and  somewliat  in.  Deviation  of  either  eye  behind 
.screen  about  efjual.  No  double  images  attainabU'.  V.  H.  -"'4,1:  witli 
+1.00  D.  •-•»/:.«.    L.  2'7,„. 


NEW  CLASSIFICATION  OF  MOTOR  ANOMALIES.  oa 

Here  the  sudden  and  excessive  upward  movement  of  tlie  left  eye 
when  directed  inward  could  only  have  been  effected  by  a  spasmodic 
contraction  of  the  inferior  oblique;  the  superior  rectus  acting  but 
slightly  as  an  elevator  when  the  eye  is  adducted. 

A  similar  case  in  which  with  paralysis  of  the  R.  externus 
and  R.  superior  rectus  there  was  spasm  of  the  R.  superior 
oblique  is  the  following: 

Emma  D.,  aged  15.  Strabismus  since  scarlatina  eleven  years  \)e- 
fore.  Occasional  vertigo;  no  diplopia.  Movements  of  L.  eye  nor- 
mal. R.  eye  cannot  move  at  all  to  right,  nor  upward  and  to  right ; 
movement  upward  almost  normal  when  eyes  are  carried  to  left  (re- 
tention of  power  of  inferior  oblique) ;  movement  downward  excess- 
ive, especially  when  eyes  are  directed  to  left  (excessive  action  of 
superior  oblique) ;  when  attempt  is  made  to  move  eyes  straight  to 
left,  R.  eye  shoots  obliquely  down  and  to  the  left  (spasmodic  action 
of  superior  oblique). 

In  addition  to  these  cases  in  which  spasm  was  associated 
with  paralysis,  I  have  seen  others  in  which  a  deviation 
limited  to  one  portion  of  the  field  of  fixation  was  present, 
which  deviation  was  always  marked  but  yet  varied  so  irnirh 
ill  amount  from  one  time  of  observation  to  another  as  to 
necessitate  the  assumption  of  its  being  spasmodic  rather 
than  paralytic  in  origin. 

Symptoms  and  Differential  Diagnosis  of  the  Different 
Varieties  of  Muscular  Over=action  and  Under=action.  No 
attempt  will  be  made  here  to  go  at  all  fully  into  the  symp- 
toms produced  by  insufficiency  or  over-action  of  the  indi- 
vidual muscles.  This  has  already  been  done  in  various 
excellent  treatises.  I  will  simply  give  the  following  facts 
to  which,  as  I  conceive,  too  little  attention  has  been  paid. 

1.  In  the  deviations  considered  in  the  foregoing  para- 
graphs the  abnormality,  as  has  been  pointed  out,  may 
affect  either  the  muscle  itself,  its  tendon,  or  the  nerve  and 
nerve-nucleus  supplying  it;  /.  e.  the  muscle  may  act  above 
or  under  the  normal  either  because  it  is  itself  too  much  or 
too  little  developed  (Structural  Deviation)  ;  or  because  the 
direction  and  insertion  of  its  tendons  are  not  what  they 
should  be  (Insertional  Deviation) ;  or  because  the  muscle 
is  in  a  state  of  paralysis  or  spasm  (Innervational — Paretic 
or  Spastic — Deviation) .  Now  it  cannot  be  too  strongly 
insisted  upon  that  tJiese  three  varieties,  however  dissiuillar 


56  NEW  CLASSIFICATION  OF  MOTOR  ANOMALIES, 

hi  (>ri(jiii,  shoir  ill  Ijii'ir  si/mjifonis  inid  ohjiriirc  siifiis  no 
real  point  of  iUfftn^nct^.  Thus  weakness  of  the  external 
rectus,  whether  arising  from  feeble  and  arrested  develop- 
ment of  the  muscular  fibre,  or  from  mal -position  of  the 
tendon  (natural  or  produced  by  a  tenotomy),  or  from  lesion 
of  the  sixth  nerve,  gives  rise  to  the  same  symptoms  and 
offers  the  same  appearances  to  objective  examination. 
The  characters  of  the  paretic  and  spastic  deviations,  to 
be  sure,  are  generally  more  definite  and  more  striking 
than  are  those  of  the  other  anomalies  mentioned,  but 
this  is  simply  owing  to  the  fact  that  such  cases  are 
-usually  seen  early,  before  any  compensatory  changes 
have  taken  place  and  while  the  diplopia,  false  projection, 
vertigo,  and  other  symptoms  are  therefore  still  marked. 
Precisely  the  same  effect  will  be  produced  in  a  patient  with 
binocular  single  vision  if  one  of  the  tendons  is  completely 
divided.  And  in  cases  of  long  standing— particularly  in 
congenital  cases — it  is  impossible  to  say  with  certainty 
from  the  symptoms  alone  without  reference  to  the  history 
whether  faulty  innervation,  faulty  insertion,  or  faulty 
structure  lies  at  the  basis  of  the  anomaly. 

2.  Couiieniial  (Ji^viafioiis  present  several  peculiarities. 
In  the  first  place  they  cause  little  or  no  trouble  for  the  ob- 
vious reason  that  the  patient  from  his  infancy  has  learned 
to  adjust  himself  to  the  anomalous  condition  present. 
Again,  it  is  remarkable  that,  even  after  the  condition  has 
existed  for  years,  there  is  no  constant  suppression  of  the 
diplopia  such  as  occurs  in  comitant  squint,  and  further- 
more, there  is  no  tendency,  as  in  the  case  of  other  non- 
comitant  deviations,  to  a  transformation  into  a  comitant 
deviation  by  the  development  of  a  contracture  of  the  an- 
tagonists. The  reason  probably  is  that  as  the  patient  has 
never  known  any  different  condition  from  that  which  he 
was  born  with,  and  as  this  condition  consequently  is  the 
natural  one  for  him,  he  experiences  no  inconvenience  from 
its  continuance,  so  that  no  involuntary  tendency  is  set  up 
toward  its  rectification.  The  result  is' that  these  congenital 
deviations,  which  may  be  due  cither  to  paresis  or  to  a  struc- 
tural defect,  afford,  as  far  as  objective  signs  go,  the 
most  typical  picture  of  uncomplicated  muscular  paralysis 
that  we  can  have. 


NEW  CLASSIFICATION  OF  MOTOR  ANOMALIES.  57 

3,  Ac<iuhT<1  iitKsciiIar  (leviafioas,  on  the  other  hand, 
whether  due  to  anomalies  of  innervation  or  insertion,  al- 
ways tend  to  become  comltanf ;  this  being  affected  by  a 
gradually  developing  contracture  of  the  antagonists  when 
the  affected  muscle  is  too  weak,  and  by  a  weakening  of 
the  antagonists  when  the  affected  muscle  is  too  strong. 
It  is  thus,  probably,  that  many  cases  of  comitant  strabis- 
mus convergens  and  strabismus  divergens  are  produced ; 
and  the  few  cases  of  strabismus  sursumvergens  that  I  have 
met  with  were  apparently  all  developed  in  this  way. 

Thus  paralysis  of  the  R.  elevators,  when  not  of  congenital  origin, 
is  regularly  followed  by  spasm  of  the  R.  depressors,  causing  the 
right  eye  to  stand  lower  than  the  other  in  all  portions  of  the  field 
of  fixation.  This  process  continuing  and  the  spasm  developing  into 
a  confirmed  contracture,  the  difference  in  height  between  the  two 
eyes  (L.  hypertropia)  becomes  equal  for  all  directions  of  the  gaze; 
the  limitation  of  movement  of  the  right  eye  upward  is  compensated 
for  by  a  corresponding  increase  in  its  movements  downward:  and 
the  picture  of  a  typical  comitant  strabismus  deorsumirrffens  is  pro- 
duced. 

If  but  one  of  the  elevators,  e.  g.  the  superior  rectus,  is  paretic  the 
spasm  is  apt  to  be  confined,  in  the  first  instance  at  least,  to  the  cor- 
responding depressor,  /.  e.  the  inferior  rectus.  In  this  case  the  devi- 
ation will  become  half-comitant,  that  is,  comitant  for  movements  up 
and  down  but  not  for  lateral  movements.  Thus,  if  the  right  supe- 
rior rectus  were  the  paretic  muscle,  we  should  have  first  a  L.  hyper- 
phoria, very  marked  in  the  upper  right-hand  quadrant  of  the  field  of 
fixation  and  diminishing  rapidly,  both  when  the  eyes  were  carried 
down  and  when  they  were  carried  to  the  left.  Later,  when  spasm  of 
the  right  inferior  rectus  had  developed,  the  L  hyperphoria  would 
become  pronounced  in  the  lower  right-hand  quadrant  also,  and  ulti- 
mately so  much  so  that  whether  the  eyes  were  carried  up  or  down, 
the  right  eye  would  always  stand  about  the  same  distance  below  the 
left.  But  in  both  the  upper  and  lower  portions  of  the  field  the  L. 
hyperphoria)  would  still  increase  as  the  eyes  were  carried  to  the  right 
and  diminish  to  zero  as  they  were  carried  to  the  left;  so  that  even 
under  these  circumstances  the  deviation  would  not  be  comitant  for 
lateral  movements. 

A  case  of  this  sort,  in  which  the  inferior  rectus  was  the  muscle 
primarily  affected  and  in  which  semi-comitancy  was  being  developed 
by  spasmodic  action  of  the  superior  rectus  has  already  been  men- 
tioned (under  the  head  of  Spasm  of  the  Ocular  Muscles). 

Cases  in  which  a  comitant  (and  even  an  alternating)  lateral  squint 
has  developed  out  of  a  paresis  of  the  externus.  folloAved  by  contract- 
ure of  the  internus  and  later  by  partial  restoration  of  the  power  of 


58  NEW  CLASSIFICATION  OF  MOTOR  ANOMALIES. 

the  externus,  have  been  repoi-ted  by  Spieer  ("Rt)yal  London  Ophth. 
Hosp.  Reports,"  xiv.  1,  18J)o),  I  liave  observed  analogous  cases, 
])arti('ularly  <>iie  in  which  a  partial  oculomotor  paralysis  with  second- 
ary contracture  of  the  externus  had  resulted  in  a  nearly  coniitant 
strabismus  divergens. 

In  proportion  as  the  deviation  becomes  transformed  from 
a  non-oomitant  to  a  comitant  one,  the  symptoms  grow  less 
disturbing;  for,  as  already  stated,  it  is  always  the  case 
that,  other  things  being  equal,  a  comitant  deviation  will 
give  less  trouble  than  will  one  that  is  non -comitant. 

4.  The  ilia(iii(>sis  Intween  ocer-adiou  and  Hn<Jer-<(rii<>n  is 
often  difficult.  Theoretically,  over-action  (spasm)  is  asso- 
ciated with  excessive  movement,  and  under-action  (pare- 
sis) with  very  deficient  movement  in  some  one  direction. 
But,  unless  the  paralysis  is  nearly  total  or  the  spasm  is 
great,  it  is  not  always  easy  to  say  whether  it  is  the  muscle 
of  one  eye  that  is  under-acting  or  whether  it  is  the  asso- 
ciated antagonist  of  the  other  eye  that  is  over-acting;  and 
when  secondary  changes  have  taken  place,  transforming 
the  deviation  into  a  comitant  one,  the  diagnosis  is  often 
impossible. 

Before  this  has  occurred  the  differentiation  may  be  made 
from  the  following  considerations. 

OVKR-ACTIOX.  I  INDKK-ACTIUN. 

Points  in  Common. 
One  eye  moves  faster  and  further  than  the  other  \vhen  both  are 
carried  in  some  one  particular  direction:  and  this  discrepancy  be- 
tween the  position  of  the  eyes  and  also  the  diplopia,  false  projec- 
tion, and  vertigo  become  more  and  more  pronounced,  the  further  the 
eyes  are  carried  in  tliat  direction.  The  primary  i)ositi(.n  for  both 
eyes  is  nearly  the  sanu-. 

The  absolute  excursion  of  the 
faster  moving  eye  in  the  given 
direction  is  greater  than  normal; 
that  of  the  other  eye  is  normal. 

The  total  excursion  of  the  fast- 
er moving  eye  in  the  given  direc- 
tion and  in  its  opposite  is  greater 
than  normal:  /.  <.,  the  field  <)f 
fixation  is  excessively  large  in  one 
of  its  diameters. 

Fixation  is  usually  perfornu'd 
l)y  the  slower  moving  eye. 

The  amount  of  deviation  may 
show  gr«'at  and  sudden  changes 
fr()m  time  to  time. 


The  al)solute  I'xcursion  of  the 
faster  moving  eye  is  n()nnal  in  all 
directions:  that  of  the  other  eye 
is  subnormal. 

The  total  excursion  of  the  fast- 
er moving  I'ye  is  normal,  that  of 
the  other  eve  is  subnormal;  /.  c, 
the  field  of  fi.xation  of  the  latter 
is  contracted  in  one  of  its  diame- 
ters. 

Fixation  usually  performed  by 
the  faster  moving  eyi'. 

The  amount  of  deviation  re- 
mains constant  or  changes  slowly 
aiul  pi'ogressiveiy. 


NEW  CLASSIFICATION  OF  MOTOR  ANOMALIES.  59 

5.  While  the  diagnosis  of  a  marked  underaction  of  one  of 
the  ocular  muscles  usually  presents  no  difficulty,  there  is 
quite  a  large  number  of  cases  in  which  the  condition  is  not 
so  obvious,  the  weakness  of  the  nuiseles  beiiiy  eoinpavatively 
sjiqhf.*  In  these  cases  diplopia  does  not  occur  until  the 
eyes  are  removed  some  distance  (10"  to  20°)  from  the  pri- 
mary position.  As  soon  as  it  does  appear,  however,  it 
develops  in  a  perfectly  typical  fashion,  showing  marked 
increase  in  some  one  special  direction  and  diminishing 
elsewhere  to  zero.  Most  cases  of  this  sort  of  anomaly,  that 
I  have  observed,  have  been  those  in  which  there  was  a 
pretty  pronounced  weakness  (perhaps  of  congenital 
origin  or,  rather,  due  to  non-development)  of  the  superior 
rectus ;  less  frequently  the  inferior  rectus  seemed  involved. 
The  nature  and  course  of  these  cases  have  not  been  thor- 
oughly investigated,  but  it  is  noticeable  that  they  are 
frequently  associated  with  a  convergence -insufficiency 
which  shows  a  tendency  to  go  over  into  a  divergence - 
excess,  resulting,  in  sone  instances  at  least,  in  a  regular 
divergent  squint.  The  chief  symptoms  (which,  however, 
are,  very  likely,  attributable  to  the  convergence-insuffi- 
ciency) are  conjunctival  irritation,  asthenopia  (often  very 
marked),  headache,  and  diplopia.  In  many  cases  the 
symptoms  are  insignificant  and  this  fact '  coupled  with  the 
absence  of  diplopia  in  the  primary  position  is  probably  the 
reason  why  these  cases  have  been  left  uninvestigated. 
Quite  a  number  of  cases  of  hyperphoria  doubtless  belong 
to  this  category. 

Another  variety  of  muscular  weakness,  transitory  in  its 
character,  is  that  already  referred  to  as  associated  with 
neurastJienia.  Here  we  may  find  diplopia  all  round  the 
periphery  of  the  field  of  fixation,  i.  e.  within  35°  of  the 
primary  position  (Concentric  contraction  of  the  field  of 
binocular  single  vision).  This  condition  would  appear  to 
have  little  significance  except  as  a  diagnostic  sign  of  the 
condition  with  which  it  is  associated. 

It  is  not  unlikely  that  slight  degrees  of  muscular  sjjasm 
are  at  the  bottom  of  some  of  the  cases  of  heterophoria  that 
we  meet  with;  e.  </.  spasm  of  either  one  of  the  elevators 

*It  is  to  these  cases  that  the  old  term  muscularlinsufficiency  should  be  limited. 


60  NEW  CLASSIFICATION  OF  MOTOR  ANOMALIES. 

or  of  either  one  of  the  depressors  may  occasion  a  hyper- 
phoria of  more  or  less  varying  character  (Spastic  lietero- 
phoria).  I  have  notes  of  five  or  six  cases  in  which  the 
presence  of  a  varying  and  even  alternating  hyperphoria 
seemed  to  be  due  to  more  or  less  spasmodic  contraction  of 
the  vertical  muscles. 

Finally  it  is  quite  likely  that  a  large  number  of  cases  of 
slight  deviation  are  due  to  moderate  nnder'arttoii  of  one 
muscle  conihhied  in'th  orer-action  (secondary  spasm)  of 
another,  so  as  to  produce  a  more  or  less  comitant  deflec- 
tion. Probably  most  of  the  cases  of  hyperphoria,  in 
which  the  deviation,  although  moderate  in  amount,  is 
present  through  the  whole  field  of  fixation,  are  attributable 
to  combined  anomalies  of  this  sort  (comitant  hyperpliona ). 
Cases  of  this  kind  often  give  rise  to  asthenopia,  headache, 
neuralgia,  and  sometimes  to  gastric  disturbance  and  im- 
pairment of  nutrition.  Diplopia  is  infrequent  and  when 
present  can  usually  be  readily  overcome. 

6.  The  diagnosis  of  the  muscles  affected  in  a  case  of 
paralysis  or  spasm  is  readily  accomplislit^d  hji  means  of  the 
donhh'  imaijes  if  the  following  principles  are  kept  in  mind. 

(a)  The  diplopia  increases  progressively  as  the  eyes  are 
carried  in  that  direction  in  which  the  action  of  the  muscle 
affected  is  normally  most  pronounced. 

(b)  Paralysis  of  any  given  muscle  of  one  eye  produces 
diplopia  of  the  same  character  and  increasing  in  the  same 
way  as  does  a  spasm  of  the  associated  antagonist  in  the 
other  eye. 

(c)  While  paresis  or  spasm  of  one  of  the  vertical  mus- 
cles does  produce  lateral  diplopia,  this  diplopia  maybe  and 
often  is  neutralized  by  the  existence  of  other  factors,  so 
that  it  is  of  no  practical  significance  in  the  diagnosis. 
The  latter  must  rest  solely  upon  the  difference  in  height  of 
the  double  images  and  the  portion  of  the  field  where  this 
difference  is  most  pronounced. 

This  fact,  emuiciatt'd  and  explained  very  elearly  by  Mauthner,  is 
frequently  overlooked,  many  insistiuK  that  paresis  of  the  superior 
and  inferior  recti  must  produce  crossed,  and  paresis  of  the  obliques 
homonymous  diplopia.  But,  apart  from  the  fact  that  these  pareses 
are    often    asso<'iated     with     cxophoria    or    esoplioria    of    sufficient 


NEW  CLASSIFICATION  OF  MOTOR  ANOMALIES. 


61 


amount  to  neutralize  their  lateral  diplopia,  the  natural  tendency 
which  the  visual  axes  display  to  diverge  when  the  eyes  are  directed 
up  and  to  converge  when  they  are  directed  down  will  work  to  aljro- 
gate  the  homonymous  diplopia  due  to  a  paresis  of  the  inferior  oblique 
and  the  crossed  diplopia  due  to  a  paresis  of  the  inferior  rectus.  As 
a  matter  of  fact  I  have  found  paresis  of  the  superior  and  inferior 
recti  often  associated  wdth  homonymous  diplopia. 

The  following  table,  constructed  in  accordance  with  the 
three  principles  just  enunciated,  shows  succinctly  the  way 
in  which  the  diagnosis  can  be  made  from  the  double 
images. 

DIAGNOSTIC   TABLE 

of  Faralysis  and  Spasm  of  the  Ocular  Muscles. 

Note,  DII  =  homonymous  diplopia;  DX  =  crossed  diplopia;  DR. 
=  vertical  diplopia  with  the  image  formed  by  the  right  eye  below ; 
DL  =  vertical  diplopia  with  the  image  formed  by  the  left  eye  be- 
low. Eu,  Ed,  Er,  El,  Eu  &  r,  etc.,  =  associated  parallel  move- 
ments in  which  the  eyes  are  directed  respectively  up  (Eyes  up) 
down,  right,  left,  up  and  right,  etc.  >>  =  increasing;  <<  =  de- 
creasing. 


Diplopia 

=  Paresis  of 

OR  =  Spasm  of 

Er.  DII           >>  greatly. 

R.  E'i;ternal  Rectus 

L.  Internal  Rectus 

Er.  DX 

L.  Internal  Rectus 

R.  External  Rectus 

El.  DII 

L.  External  Rectus 

R.  Internal  Rectus 

El.  DX 

R.  Internal  Rectus 

L.  External  Rectus 

Eu.  &r.  DL     " 

R.  Superior  Rectus 

L    Inferior  Oblique 

Eu.  &r.  DR     ■' 

L.  Inferior  Oblique 

R.  Superior  Rectus 

Eu.  &1.  DR      " 

L.  Superior  Rectus 

R.  Inferior  Oblique 

Eu.  &1.  DL      " 

R.  Inferior  Oblique 

L.  Superior  Rectus 

Ed.  &r.  DR     " 

R.  Inferior  Rectus 

L-  Superior  Oblique 

Ed.  &  r.  DL      " 

L.  Superior  Oblique 

R.  Inferior  Rectus 

Ed.  &1   DR      " 

R.  Superior  Oblique 

L.  Inferior  Rectus 

Ed.  &1.  DL      '• 

L.  Inferior  Rectus 

R.  Superior  Oblique 

The  above  table  is  sufficient  for  all  ordinary  working 
purposes,  but  or  the  sake  of  coi-ppleteness  I  grve  also  the 
more  extensive  one  subjoined,  which  I  have  devised  to 
show  how  the  character  of  the  diplopia  may  be  modified 
by  circumstances. 


62  NEW  CLASSIFICATION  OF  MOTOR  ANOMALIES. 

TABLE  OF  DIPLOPIA. 

A.      HOMOXYMOrs  DIPLOPIA  VARYIN(t  WITH   DIFKKKKNT  DIRKCTIONS 
OF  THE    UAZK. 

/.    Vtiridtion  f/reat  =  Paresis  of  Externus  (Sjkisiii  of  Internns.) 


CHARACTER  OF  DIPLOPIA 

INDICATES  PARESIS 
OF 

OR  SPASM   OF 

DII  >>  in  Er,  <<  in  El. 
DII  »  in  El.  <<  in  Er. 

R.  External  Rectus 
L.  External  Rectus 

L.  Internal  Rectus 
R.  Internal  Rectus 

II.    Variation  slifjht  =  Paresis  of  Oblique  (Spasm  of  Sii])erior  or  In  ft 

rior  Bectus)  or  a  couiitant  esojthoria  <(ssociate<l  irifli  a  conditio)) 

'caiisinf/  rarijiiuj  1)X. 


f  Particularlv  marked   in!  (  R.    Inferior  Oblique 
niT  >  >  in  Vr    I  K"-  iKu.  &  r.]  I  R.  Superior  Rectui 

uii  <"r-  111  r,r.   i  Particularly  marked   in   I  R.  Superior  Obliqi 

I  Ed.  [Ed.  &  r.l  i  R.  Inferior  Rectus 


f  Particularly  marked   it 
.  ,  „,    J  Eu.  [Eu.  &  l.J 
"'    •      I  Particularly  marked   ir 
Ed.  [Ed.  &1.J 


f  L.  Inferior  Oblique 
"I  L.  Superior  Rectus 
J  L.  Superior  Oblique 
1  L.  Inferior  Rectus 


L.  Superior  Rectus 
L-  Inferior  Oblique 
L.  Inferior  Rectus 
I,.  Superior  Oblique 

R.  Superior  Rectus 
R.  Inferior  Oblique 
R.  Inferior  Rectus 
R.  Superior  Oblique 


B.      CROSSED  DIPLOPIA  VARYINU  IN   DIFFERKXT  DIRECTIONS  OF 
THE  (iAZE. 

I.    Variation  great  =  Paresis  of  Internns  (S/iasni  of  IJ.rternas.) 


CHARACTER   OF   DIPLOPIA 


DX>>  in  Er.,  <<  \r\  El. 
D>>  in  l-:i..  <<  in  Er. 


=  PARESIS  OF 


OR  SPASM  OF 


L.  Internal  Rectus      R.  External  Rectus 
R.  Internal  Rectus      I,.  External  Rectus 


//.    Vari<ttioii  sliijlit  =  Paresis  of  a  Superior  or  Inferior  Pectus  (S))t(^ 
of  an  Ohlii/iw)  or  a  comitant  e.vophoria  associated  with  a 
condition  causing  rarijinn  DII. 


I  I'arlicularly  marked    inl  I  I,.  Superior  Rectus     I  K.  Inferior  Oblique 

UX  >>     n  Er.    ',  Eu.  lEu.  &  r.)  I  L.  Superior  Obliciue  I  K.  Superior  kectusi 

<<  in  El.    1  Particularly  marked  in  \  I,.  Inferior  Rectus      I  K.  Superior  Oblique 

I  Ed.  Ed.  it  r.l  (  I,.  Superior  (>bli(|i:e    K.  Inferior  Rectus 

(  Particularly  marked   in  (  R.  Superior  Rectus      L-  Inferior  Oblique 

n.\  >>  in  I-;i.    J  V.u    [Eu.  &1.1  1  K.  Inferior  Oblique     U.  Superior  Rectus 

<'1inEr.    1  Particularly  marked   in  f  R.  Ir  ferior  Rectus       I..  Superior  t)blique 

I  E<1.  [I'M.  &  l.j  I  K.  Superior  Obli(|Ue    I,.  Inferior  Rectus 


NEW  CLASSIFICATION  OF  MOTOR  ANOMALIES. 


63 


C.    VERTICAL  PTPLOPIA  VARYING  IN   DIFFERENT   DIRECTIONS   OF   THE 
GAZE   (=  PARESIS  OR  SPASM  OP  ELEVATOR  OR  DEPRESSOR.) 

1.  Diplopia  ^^  in  Eii.  (Paresis  or  Spasm  of  Elerator.) 


CHARACTER  OF  DIPLOPIA 


1DR.  most  marked  in  Eu. 
&  r.  I  regularly  associ- 
ated with  DII  >>  iu 
DR.  most  marked  in  Eu. 
&  1.  [regularly  associ- 
I  ated  with  DX  >  >  in 
I  Eu.  &  r.]  I 


PARESIS  OF 


OK  SPASM  OK 


I,.  Inferior  Oblique     R.  Superior  Rectus 

1 
L.  Superior  Rectus     R.  Inferior  Oblique 


f  DL  most  marked  in  Eu. I     R.  Superior  Rectus     L,  Inferior  Oblique 
1    &  r.    [regularly  associ" 


I    ated    with    DX    > 
,^,       ,    ....       1    Ru.  &1.] 
Y>h,  K-  K-  in  hA\.  -^  jjj^  j^Qg^  marked  in  Eu. 

I    &  1.    [regularly  associ- 

I    ated   with   DII    >  >    in 

I    Eu.  &r.] 


R.  Inferior  Oblique     L.  Superior  Rectus 


II.  Diplopia  U^  in  Ed.  (=  Paresis  or  Spasm  of  Depressor). 


!DR  most  marked  in  Ed. I     R.  Inferior  Rectus      ^I..  Superior  Oblique 
&  r.    [regularly  associ-] 
ated    with   DX    >>    in  1 

DR  most  marked  in  Ed.j     R.  Superior  Oblique   L.  Inferior  Rectus 
1    &  1.  regularly  associat-'  ' 

ed  with  DII  >>  in  Ed.i 
I   &r.]  1 

[  DL  most  marked  in  Ed.      L.  Superior  Oblique   R.  Inferior  Rectus 
1  -&  r.    [regularly   associ-' 
I    ated    with   DII    >  >    in 

DI,  >  >  in  Ed     |  p^  niost  marked  in  Ed.'     L.  Inferior  Rectus       R.  Superior  Oblique 
I    &  1. regular   associated 
I    with  DX>>inEd.  &  r.  


From  the  foregoing  table  the  following  facts  are  appar- 
ent: 

(1)  All  Jiomonyinous  diplopia,  whether  laiye  or  .'<niaU, 
irhich  increases  as  the  eyes  are  carried  to  the  right  indicates 
niider'action  of  SOME  muscle  of  the  ru/ht  ei/e  or  over-nrtioii 
of  SOME  muscle  of  the  left. 

(2)  A  crossed  diplopia  which  increases  as  the  ei/es  are  car- 
ried to  the  right  indicates  nnder-action  of  SOME  muscle  of 
fJi(^  left  e//e  or  ovcr-acfion  o/"  some  muscle  of  the  rhjht. 

Treatment  of  Anomalies  of  the  Individual  Muscles.  1.  In 
every  case  of  over-action  or  under-action  of  the  muscles 
our  first  attempts  must  be  directed  to  removing  the  cause  of 


64  NEW  CLASSIFICATION  OF  MOTOR  ANOMALIES. 

the  trouble.  This  is  effected  with  more  or  less  success  in 
syphilitic  paralysis  and  in  the  paralysis  caused  by  the 
pressure  of  meningitic  effusions  upon  the  nerves  when  we 
employ  the  iodides  and  mercury;  in  the  so-called  rheu- 
matic paralysis,  due  apparently  to  exposure  to  cold,  when 
we  use  sodium  salicylate  and  the  iodides;  and  when  in 
hysterical  disorders  we  employ  the  appropriate  moral 
treatment. 

2.  When  the  cause  is  unknown  or  cannot  be  reached,  an 
(xpecfant  treatment  combined  with  corroborrnif  ineasiins 
(especially  open-air  exercise)  must  be  employed.  This  is 
particularly  the  course  to  be  pursued  in  spastic  deviations, 
in  hysterical  and  diphtheritic  paralysis,  and  in  the  limita- 
tion of  the  movements  of  the  eye  due  to  neurasthenia. 

The  use  of  strychnine,  advocated  by  some  as  bein^  a  direct  tonic 
for  insufficient  muscles,  seems  to  be  efficient  only  so  far  as  it  acts  to 
iinprove  the  patient's  general  condition.  The  same  may  be  said  of 
I'lectricity. 

3.  When  the  deflection  is  slight,  confirmed,  and  espe- 
cially if  it  is  more  or  less  comitant,  prisutK  often  do  good 
service,  particularly  in  the  vertical  deviations. 

In  the  lateral  deviations  they  are  of  less  service,  because  these  are 
frequently  complicated  by  the  presence  of  divergence  or  convergence 
anomalies,  in  which  tlie  prolonged  use  of  prisms  is  distinctly  injur- 


ious. 


4.  Operaiive  nica.sures  are  to  be  adopted  only  when  we 
are  assured  that  the  condition  has  reached  a  stage  in  which 
it  is  no  longer  likely  to  undergo  change.  Even  in  long- 
standing cases  of  paralysis  it  may  be  dangerous  to  oper- 
ate, since  the  paralysis  may  disappear  even  after  lasting 
for  months,  and  then  the  operation  which  previously  suf- 
ficed to  correct  the  deviation  will  now  over-correct  or  pro- 
duce a  deviation  in  the  opposite  sense  which  may  be  worse 
than  the  original  one. 

On  the  other  hand,  the  judicious  division  of  a  contractured  unpar- 
alyzed  nuisde  may  by  giving  the  paraly/.«'d  muscK»  more  play  assist 
in  restoring  tlie  power  in  tlie  latter.  See  two  case's  l)y  Chi'vaHercau 
(Trans,  of  Vlll.  Internat.  Ophth.  Congress,  Edinburgli,  1H!»4)  in 
which  the  movements  of  an  eye  the  subject  of  a  partial  oculomotor 
paralysis  were  restored  by  tenotomy  of  the  unparalyzi'd  extenuis. 
These  cases  are  analogous  to  those  iji  whicli  the  power  of  the  extend, 
weakened  l.y  p.-rsistenl  .M.iilracliire  of  interni  due  to  a  .•onvergence- 


NEW  CLASSIFICATION  OF  MOTOR  ANOMALIES.  65 

spasm,  is  gradually  restored  by  the  very  prolonged  use  of  the  propei- 
correcting  glasses  which  relieve  the  spasm  and  allow  the  extern!  to 
act  more  freely.  (See  Long  and  Barret's  eases,  cited  in  section 
YII.) 

In  any  case  care  must  be  taken  that  the  app)'<ypriate  op- 
eration is  performed.  The  principles  of  operating,  which 
were  admirably  enunciated  by  A.  Graefe,  may  be  thus 
stated : 

Over-acfion  of  a  muscle  is  to  be  relieved  by  tenotomy  of 
the  over-acting  muscle.  JJnder-action  is  to  be  relieved  by 
tenotomy  of  the  associated  antagonist  to  the  under- acting 
muscle,  or,  where  this  is  impracticable,  by  advancement  of 
the  under-acting  muscle  itself.  Sometimes,  especially  in 
paralysis  of  the  externus  and  internus,  these  operations 
have  to  be  further  reinforced  by  tenotomy  of  the  direct  an- 
tagonist of  the  paralyzed  muscle. 

The  reason  for  these  rules  is  obvious.  When  a  muscle  is  too  strong 
we  can  reduce  its  action  more  or  less  effectively  by  a  tenotomy.  If 
the  muscle  is  too  weak,  but  yet  retains  some  of  its  power,  we  can 
increase  this  power  by  performing  an  advancement.  If,  however, 
the  muscle  has  lost  all  power,  an  advancement  is  obviously  futile, 
and  if  the  muscle  acts  biit  little  an  advancement  alone  is  generally 
insufficient.  Then  we  have  only  to  remember  that  when  a  muscle  is 
too  weak,  the  effect  upon  the  movements  of  the  two  eyes  is  the  same 
as  if  the  associated  antagonist  in  the  other  eye  was  too  strong;  and 
if  we  tenotomize  this  antagonist,  we  shall  limit  the  movement  of  the 
sound  eye  in  the  same  sense  and  to  the  same  extent  as  that  in  which 
the  movement  of  the  affected  eye  is  already  limited,  /.  e.  both  ej-es 
will  again  move  equally  with  each  other,  although  the  movement  of 
neither  will  be  normal.  If  no  secondary  changes  have  taken  place, 
tenotomy  of  the  associated  antagonist  alone  may  suffice,  but  usually 
the  weakened  muscle  is  opposed  by  a  contractured  and  hence  over- 
acting mviscle  in  the  same  eye  (direct  antagonist),  and  therefore  we 
may  have  also  to  divide  the  latter  in  order  to  secure  the  proper  bal- 
ance of  action. 

For  the  particular  cases  these  rules  may  be  expanded  as 
follows : 

Under-actlon  of  the  B.  externus  indicates  tenotomy  of  the 
L.  internus,  usually  combined  with  advancement  of  the  R. 
externus  and  often  with  tenotomy  of  the  R.  internus. 

Under-aetion  of  t lie  li.  in teriiu.s  requires  advancement  of 
the  R.  internus  combined  with  tenotomy  of  both  externi. 

The  advancement  in  this  case  is  imperatively  demanded,  because 
the  internus  has  to  be  used  in  conA'ergence  as  well  as  in  associated 
5 


66  NEW  CLASSIFICATION  OF  MOTOR  ANOMALIES. 

imrallel  moveinent.s.  For  the  latter  it  might  aet  .suffieieiitlv  well,  eevn 
if  intrinsically  weak,  provided  the  externiis  of  the  other  eye  was  also 
weakened  and  to  the  same  extent:  but  for  the  proper  performance 
of  eonvergrence  movements  the  interniis  reiiuires  to  he  intrinsically 
strong:,  which  can  be  effected  only  by  an  advancement, 

Vnder-action  of  the  H.  superior  ohlique  requires  tenotomy 
of  L.  inferior  rectus.  This  operation  gives  very  satisfac- 
tory results. 

Under-avtion  of  the  R.  inferior  oblique  ve(\\i\pes,  tenotomy 
of  the  L.  superior  rectus. 

Under-avtion  of  tJie  R.  superior  rectus  is  in  general  best 
remedied  by  advancement  of  the  muscle  itself.  If  there  is 
secondary  contracture  of  the  inferior  rectus,  the  latter  may 
be  divided  also,  but  this  operation  should  be  performed 
with  considerable  caution  owing  to  the  unpleasant  effects 
produced  by  insufficiency  of  any  one  of  the  depressor 
muscles. 

In  very  slig:ht  cases  of  insufficiency  of  the  superior  rectus  in  which 
the  increase  of  the  diplopia  in  lateral  directions  of  the  gaze  would 
not  be  very  great,  and  in  which  the  aim  is  simply  to  remove  the  mod- 
erate hyperphoria  in  looking  straight  ahead,  cautious  tenotomy  of  the 
siiperior  rectus  of  the  other  eye  may  replace  the  operation  of  ad- 
vancement. 

Lender-action  of  the  R.  inferior  rectus  requires  advance- 
ment of  the  muscle  itself,  which  may  need  to  be  supple- 
mented by  tenotomy  of  the  R.  superior  rectus. 

Over-action  of  eitJier  one  of  the  four  recti  is  remedied  by 
advancement  of  the  over-acting  muscle. 

Over-action  of  the  R.  superior  oblique  calls  for  advance- 
ment of  the  L.  inferior  rectus.  In  very  slight  cases  this 
operation  may  be  replaced  by  a  cautious  tenotomy  of  the 
R.  inferior  rectus. 

Over-action  of  the  R.  inferior  oblique  is  relieved  by  ad- 
vancement of  the  L.  superior  rectus  or,  in  very  slight  cases, 
tenotomy  of  the  R.  superior  rectus. 

It  is  probably  from  a  failure  to  conform  to  these  principles  that  a 
large  pai't  of  the  disappointment  occasioned  by  the  results  of  tenoto- 
mies done  for  lieterophoria  is  due.  For  example,  a  L.  hyperphoria 
due  to  insuthciency  of  a  R.  elevator  nuisde  is  treated  by  tenoto- 
mizing  the  R.  inferior  rectus.  This  operation  does  not  essentially 
relieve  the  litiiitation  of  movenu-nt  in  the  upper  Held,  which  really 
caused  the  hyperphoria  and  niost  likely  the  symptoms  ascribed  to  the 
latter;   on  the  coiitrarv,  it   adds   to   tli<'   condition   already  (>xisting  a 


NEW  CLASSIFICATION  OF  MOTOR  ANOMALIES.  67 

new  and  very  troublesome  patliolof^ical  eoiidition,  namely,  a  limita- 
tion of  the  movements  of  the  right  eye  in  the  lower  tield  also.  In 
other  words,  to  the  paresis  already  present  another  paresis  has  been 
added  l)y  oi)eration,  and  the  patient  suffei's  from  the  eoml)ined  effects 
of  l)oth.  That  the  «^ffeet  of  both  pareses  actually  eo-exist  can  readily 
be  demonstrated  by  an  examination  of  the  double  images.  It  will  be 
found  that  the  diplopia  in  the  upper  field  has  not  been  materially  re- 
duced by  the  operation,  while  a  diplopia  which  did  not  exist  l)efore 
has  been  introduced  into  the  lower  field  and  gives  rise  to  nnich  dis- 
turbance. In  this  case  advancement  of  the  weak  elevator  in  the  af- 
fected eye  or  tenotomy  of  the  elevator  in  the  other  eye  would  be  the 
proper  operation. 

Parakineses.  Tremor  of  Individual  Ocular  Muscles  (Uni= 
lateral  or  Non=symmetrical  Nystagmus).  The  tremulous 
movement  (alternating  spasm)  that  we  denote  by  the  name 
of  nystagmus,  although  usually  affecting  equally  the  asso- 
ciated muscles  in  the  two  eyes,  and  therefore  dependent  in 
all  probability  upon  a  lesion  of  the  association-centers,  may 
be  confined  to  the  muscles  of  one  eye  or  be  of  a  different 
character  in  one  eye  from  that  in  the  other. 

Hence,  while  ordinarily  constituting  a  perversion  of  the 
associated  parallel  movements  of  the  eyes,  in  these  cases 
it  must  be  regarded  as  a  perversion  of  the  movements  of  the 
individual  muscles.  These  cases,  are,  to  be  sure,  quite 
rare.  Graefe  (Graefe-Saemisch)  reports  four  cases  of  uni-^ 
lateral  vertical  nystagmus  (two  observed  by  himself) ,  and 
adds  that,  while  he  has  seen  cases  of  slight  rotary  nystag- 
mus confined  to  one  eye,  he  has  never  met  with  one  of  uni- 
lateral horizontal  nystagmus.  Frost,  however  (Trans. 
Ophth.  Soc.  of  United  Kingdom,  xiv.  245),  reports  a  case 
of  acquired  nystagmus  in  which  the  oscillations  were  hori- 
zontal in  one  eye  and  vertical  and  rotary  in  the  other. 


VI. 

ANOMALIES  OF  ASSOCIATED  PARALLEL  MOVEMENTS. 

Hypokineses.  Paresis  and  Insufficiency  of  Associated 
Parallel  flovements.  rarali/si.s  of  the  lafemJ  associated 
iiioccinrnts  of  the  eyes  is  not  infrequent  in  destructive  cer- 
ebral disease,  particularly  apoplexy,  the  site  of  the  lesion 
in  paralysis  of  dextroversion  being  in  the  left,  and  in  par- 


68  NEW  CLASSIFICATION  OF  MOTOR  ANOMALIES. 

alysis  of  sinistroversion  in  the  right  half  of  the  brain.  In 
pure  cases  of  this  sort  the  power  of  convergence  is  re- 
tained, showing-  that  the  internal  rectus,  although  incapaci- 
tated as  far  as  consentaneous  action  with  the  opposite 
externus  is  concerned,  is  not  disabled  from  performing 
work  in  conjunction  with  its  fellow  internus.  This  shows 
that  in  these  cases  we  are  not  dealing  with  a  conjoined 
paralysis  of  one  externus  and  one  internus,  but  with  an 
inhibition  of  one  particular  hioreiiioii  of  the  two  eyes. 

Parabisix  of  sursmiivermon  (without  any  involvement  of 
the  lateral  movements)  and  para/ >/.s/,^  of  .sursta/iverKt'oii  a)i(( 
deorsumi'ersion  (of/efher  have  been  observed  (Gowers; 
Sauvineau,  Trans,  of  VIII.  Ophth.  Congress,  Edinburgh, 
1894) . 

Except  as  diagnostic  signs  of  the  condition  causing  them 
these  associated  deviations  are  of  little  clinical  importance. 
Whether  there  are  slighter  grades  of  these  disorders,  not 
dependent  upon  severe  structural  disease  and  possibly 
productive  of  more  symptoms  on  their  own  account,  has 
not,  as  far  as  I  know,  been  positively  demonstrated. 

Certain  cases,  however,  described  by  Savag-e  (Oph.  Record. 
Jan.,  1896)  under  the  name  of  Asthenic  vertical  orthophoria 
in  which  the  combined  up-and-down  movements  of  botli  eyes 
(sursum  version  and  deorsum  version)  were  performed  insuffi- 
ciently and  with  difficulty  wouUl  seem  to  belong'  in  tliis  cate- 
gory; and  possibly  the  explanation  of  the  conditions  called  by 
Stevens  Anatropia  and  Catatropia  nuiy  l)e  had  by  assuming  a 
weakness  of  deorsumversion  in  the  former  case  and  of  sursumversion 
in  the  latter,  so  that  in  either  instance  both  visual  lines  are-  off  tlie 
proper  level  (see  Section  IX). 

Hyperkinesis.  Spasm  of  Associated  Parallel  riovements. 
Spasm  of  the  associated  lateral  movements  producing 
deviation  of  both  eyes  to  the  right  (Spastic  dextroversion) 
or  to  the  left  (Spastic  sinistroversion)  is  not  infrequently 
observed  as  the  result  of  irritative  lesions  of  the  brain. 
Deviation  to  the  right  is  produced  by  disease  of  the  left 
side  of  the  brain  and  vice  vrrsa. 

Spasm  of  associated  movements  (particularly,  combined 
vertical  and  lateral  spasm,  producing  oblique  deflections 
of  both  visual  lines)  also  occurs  as  a  transient  and  par- 
oxysmal manifestation  in  epilepsy  and  hysteria. 


NEW  CLASSIFICATION  OF  MOTOR  ANOMALIES.  69 

Tlie  fuvious  case  described  by  Frost  (Trans.  Ophtli.  Soc.  United 
Kingdom),  in  which  there  was  spastic  deviation  of  both  eyes  down 
and  to  the  right,  but  in  which  there  Avas  no  actual  impairment  of  the 
movements  of  either  eye  by  itself,  was  apparently  hysterical  in 
character. 

The  following  peculiar  case  of  a/fernafing  spasm  of  asso- 
rlafed  parallel  movements  was  apparently  choreiform  in 
character  and  would  seem  to  form  a  sort  of  connecting 
link  between  cases  of  tonic  spasm,  such  as  those  just  men- 
tioned, and  true  nystagmus. 

Ghoreiform  Spasm  of  Associated  Oblique  Movements. 
Simon  N.,  aged  13  years,  came  under  my  care  Nov.  1*2.  1S92. 
Chorea  two  years  ago.  Anemic.  Now  shows  every  few  minutes, 
especially  when  watched,  sudden  darting  movements  of  both  eyes 
upward  and  to  the  right  and  back  again.  The  return  movement 
takes  place  in  two  phases,  the  eyes  shooting  down  and  to  the  left 
somewhat  beyond  the  primary  position,  and  then  by  a  sharp  jerky 
motion  coming  up  again  to  the  latter.  If  the  gaze  is  directed  to  the 
left,  both  eyes  dart  upward  and  to  the  left  and  then  back  again.  In 
either  case,  whether  moving  up  and  to  the  right  or  up  and  to  the 
left,  the  direction  of  the  movement  is  at  an  angle  of  4.5°  with  the 
horizontal,  and  the  eyes  are  carried  up  until  the  pupils  are  three- 
quarters  buried  beneath  the  upper  lids.  Slight  choreiform  twitchings 
of  the  face  accompany  the  movements. 

Orthophoria.  No  diplopia.  Associated  movements,  although  slug- 
gish, perfectly  normal. 

V.  R.  'Vi.-.  L-  'Vto.  Under  liomatropine.  R.  +  1.00  D.  '■/,,:  L. 
+  1.50  D.  Cyl.  Ax.  85°  T.  '"7:>o. 

Three  weeks  treatment  with  arsenic  and  hydrochloric  ac-id  effected 
no  improvement.  On  Jan.  15,  18U3,  R.  +  0.  75  D.  Sph.,  L.  +  1.50 
I).  Cyl.  Ax.  85°  T.  given.  Patient  then  passed  from  observation  and 
has  not  been  seen  since. 

Except  for  the  long  interval  l)etween  the  separate  spasmodic 
movements,  the  appearances  presented  in  this  case  differ  in  no  re- 
spect from  those  observed  in  nystagmus.  Its  development,  however, 
in  a  patient  with  fair  sight  and  normal  muscles,  and  the  past  history 
and  present  evidences  of  chorea  led  me  to  regard  it  not  as  a  true 
nystagmus.  If  nystagnnis  at  all,  it  was  a  very  rare  form  of  the 
affection. 

Parakineses.  Tremor  of  Associated  Parallel  Movements 
(Nystagmus).  Nystagmus,  as  ordinarily  met  with,  con- 
sists of  an  equal  and  parallel  movement  of  the  two  eyes, 
both  executing  a  series  of  rapid  oscillations  in  the  same 
direction  and  at  the  same  time.  These  oscillations,  which 
vary  in  frequency  from  30  to  150  a  minute,  occur  in  two 


70  NEW  CLASSIFICATION  OF  MOTOR  ANOMALIES. 

phases,  a  rapid  darting  movement  first  taking  place  in  a 
certain  direction  and  this  being  followed  by  a  movement 
of  return  to  and  beyond  the  original  position  of  the  eyes. 
The  latter  or  second  phase,  although  slower  than  the  first, 
is  evidently  an  active  movement  and  not  a  mere  relaxation 
of  the  muscles  that  have  just  been  spasmodically  con- 
tracted. The  direction  of  the  movement  is  usually  from 
side  to  side  ( Jforizonfal  iii/sfagnius),  sometimes  rotary, 
both  vertical  meridians  revolving  in  the  same  direction 
(Rotary  nysfar/)ni(t< ),  and  very  rarely  vertical  (  Vertical 
ni/star/mus).  Not  infrequently  combinations  of  two,  or 
even  of  all  three  forms  are  observed  (Mixed  iit/sfaj/nitis). 

Movements  of  this  character  point  to  a  pathological  con- 
dition of  the  association-centres,  causing  the  discharge  of 
alternate  and  excessive  stimuH  from  the  latter  instead  of 
the  simultaneous  and  equal  stimuli  of  moderate  intensity, 
which  enable  the  normal  eye  to  remain  steady  in  the  posi- 
tion of  fixation. 

The  eyes  ordinarily,  when  looking  at  an  object  strai^lit  aliead  of 
them,  are  kept  in  place  by  simultaneous  contraction  of  the  opposing- 
muscles;  i.  e.  they  move  neither  to  the  right  nor  to  the  left,  bec:iuse 
they  receive  equal  and  simultaneous  impulses  from  the  cen- 
tre for  right-handed  movements  (dextroversion)  and  that  for  left- 
handed  movements  (sinistroversion). 

If,  however,  these  impulses,  instead  of  being  simultaneous,  are  al- 
ternate, so  that  the  eyes  first  receive  an  impulse  from  the  centre  for 
dextroversion  a)ul  then  one  from  the  centre  for  sinistroversion,  and 
if  these  impulses  allcniate  rapidly,  we  sliall  have  the  picture  of  hori- 
zontal nystagmus. 

A  similar  want  of  simultaneity  in  the  dischai'ge  of  impulses  from 
the  centres  for  sursumversionand  (kM)rsumversion  will  produce  a  rer- 
timl  nystagmus.  And  a  rotari/  nystagnnis  will  result  from  tiu'  tlis- 
charge'of  alternate  instead  of  simultani'ous  stinudi  from  the  centres* 
which  produce  rotati<m  of  both  vertical  meridians  to  the  right  and  to 
the  left  respectively.  Finally,  a  combniation  of  some  or  all  of  these 
anomalies  accounts  for  tlie  various  forms  of  iiiixed  nystagmus. 

This  conception  of  the  central  orif/in  of  nystagmus,  and 
more  particularly  of  its  origin  from  some  lesion  of  the  dif- 
ferent association -centres,  seems  forced  upon  us,  not  only 

♦Inferred  to  exist  from  this  very  symptom.  The  riKht-rotatinK  ceutre,  nctiiiK  by 
itself,  would  proilme  simultaneous  contraction  of  the  riRht  inferior  oblique  and  in- 
ferior rectus  and  of  the  left  superior  oblique  and  superior  rectus:  and  the  left-rotat- 
injf  centre  would  similarly  produce  contraction  of  both  inferior  muscles  ol  tlie  lelt 
and  both  superior  muscles  of  the  right  eye. 


NEW  CLASSIFICATION  OF  MOTOR  ANOMALIES.  71 

by  the  character  of  the  movements  executed,  but  also  by  a 
great  variety  of  pathological  data.  For  further  informa- 
tion as  to  the  latter,  reference  may  be  made  to  the  exhaust- 
ive articles  by  Graefe  (Graefe-Saemisch  and  Arch,  fiir 
Ophth.,  xxiv.  3,  1895). 


VII. 

ANOMALIES  OF  CONVERGENCE. 

Hypokineses.    Paralysis  and  Insufficiency  of  Convergence. 

Absolute  loss  of  power  of  convergence  with  retention  of  the 
power  of  making  associated  parallel  movements  has  been 
occasionally  observed.  Since  either  eye  can  still  be  turned 
inward  when  acting  with  its  fellow  to  move  to  the  right  or 
to  the  left,  these  cases  cannot  be  referred  to  paralysis  of 
the  interni,  but  indicate  some  lesion  of  the  convergence- 
centre,  causing  a  paralysis  of  convergence  ( PavalJeJ  sqw'nf 
of  Schneller) . 

Cases  of  this  sort  in  which  the  paralysis  was  total  or 
practically  so  (convergence  near-point  at  from  2  to  6 
metres),  have  been  described  as  well  as  others  in  which 
the  paralysis  was  marked  but  not  complete.  I  myself  have 
seen  one  case  of  the  sort. 

The  paralysis  is  frequently  associated  with  paralysis  of 
accommodation  and  in  some  of  Parinaud'sand  Sauvineau's 
cases  was  accompanied  by  paralysis  of  sursumversion 
and  deorsumversion.  One  peculiar  feature  is  that  the 
prism-convergence  (/.  e.  the  power  of  overcoming  prisms, 
base  out)  is  retained  in  some  of  the  cases  (Straub). 

The  eases  hitherto  reported  are : 

Schweigger,  Klin.  Untersiich,  iiber  das  Schielen  1881  (cited  by 
Straub)  2  cases. 

Parinaud,  Arch,  de  Neurologie,  1883  (cited  by  Sauviueau). 

Sales,  Trans.  Ophth.  Soe.  United  Kingdom,  iv.  (1884),  p.  390  (cited 
by  Gowers). 

Parinaud,  Brain,  ix.  330,  1887  (cited  by  Straub),  5  cases. 

Stolting  and  Bruns,  Arch,  fiir  Ophth.  xxxiv.  3,  1888  (cited  by 
Straub). 

Benzler,  Deutsch.  militar-aerztl.  Zeitschr.,  xviii.  (cited  by  Straub). 

Peters,  Centralbl.  f.  pract.  Augenheilk.,  xiii.  (cited  by  Straub). 


72  NEW  CLASSIFICATION  OF  MOTOR  ANOMALIES. 

Sanviiif.MU.  Ti'.-iiis.  VI II.  Iii1cni;it.  Oi)litli.  ( 'oufirt'ss.  KdiiiburKh, 
1S!»4. 

Straiib,  M.,  Arch,  of  Ophtli.,  xxv.  :i  (18%). 

Hayne,  H.  W.,  ib. 

Graefe's  10  cases  (cited  by  Straub)  come  rather  uikU'V  the  head  of 
convergence-insufficiency  than  actual  paralysis. 

Much  more  frequent  and  important  are  those  cases  in 
which  there  is  simply  a  greater  or  less  weakness  of  conver- 
gence (Convergence  =  insufficiency).  A.  Graefe,  who  re- 
garded these  cases  as  quite  rare,  gives  an  excellent  expo- 
sition of  some  ef  the  physical  signs  of  the  condition  in  a 
paper  read  before  the  Seventh  Ophthalmological  Congress 
(1888).  Tn  their  entirety  these  s/'(/its  may  be  stated  as  fol- 
lows: 

For  distance.  Lateral  orthophoria  or  slight  exophoria 
(l?-2'°)  by  all  tests  (screen,  parallax  and  phorometer) .  As- 
sociated lateral  movements  practically  normal.  Associated 
vertical  and  oblique  movements  of  ten  restricted  (frequently 
in  an  asymmetrical  manner)  and  field  of  binocular  single 
vision  often*  markedly  limited  in  some  one  direction  above 
or  below,  indicating  a  weakness  of  an  elevator  or  depressor 
(particularly  the  superior  rectus).  Diverging  power  (ab- 
duction) not  over  9",  frequently  subnormal  (5^-6).  Prism- 
convergence  (so-called  adduction)  often,  although  not 
always,  restricted,  being  acquired  with  difficulty  and  per- 
formed with  effort.! 

For  near.  Marked  exophoria  by  all  tests  (/.  r.  exophoria 
of  7^  or  over  by  both  phorometer  and  parallax,  and  notice- 
able deviation  out  behind  the  screen).  Associated  "lateral 
movements  normal.  Pc  (near  point  of  convergence)  3"  or 
over  from  the  root  of  the  nose,  and  maintenance  of  eyes  in 
position  of  extreme  convergence  for  more  than  a  moment 
difficult  or  impossible.  Convergence  near-point  about  the 
same  whether  the  object  is  approximated  from  a  point  to 
the  right  or  from  a  point  to  the  left  of  the  median  line.     If, 

*In  about  20  per  cent,  of  the  case.s  that  I  have  ob.servcd.  In  these  ca.ses  there  is 
often  hyperphoria  for  distance  in  the  primary  position. 

tThat  is.  the  primary  adduction  (t.  e  the  greatest  amount  that  the  patient  can  be 
not  to  do  at  the  first  trial)  will  be  only  8°  or  1-'",  and  the  addition  of  even  1°  or  2°  to 
this  will  produce  insuperable  diplopia.  Moreover,  the  e.xertion  of  overcouiintf  a 
prism  of  even  this  imiouut  is  associated  with  a  sense  of  strain,  and  tlie  patient,  if  he 
does  succectl  in  oviriomiiij.;  the  prism  for  a  moment,  cannot  lu>M  the  images  together. 
These  features  constituti-  a  marked  difference  from  those  obtaining  in  normal  eyes 
which,  though  they  may  have  difficulty  in  learning  to  overcome  prism--  l>:is(  out  will 
do  so  with  ease  and  with  rapidly  increasing  facility  after  a  few  trials 


NEW  CLASSIFICATION  OF  MOTOR  ANOMALIES.  73 

when  the  convergence  near-point  is  reached,  one  eye  be 
screened  and  then  th6  object  of  fixation  is  carried  still 
closer  to  the  nose,  the  uncovered  eye  will,  although  with 
difficulty,  turn  in  still  further,  in  order  to  follow  the  object, 
while  the  eye  behind  the  screen  will  diverge  by  an  equal 
amount  (preservation  of  associated  adduction,  failure  of 
convergence -adduction. — Graefe). 

Graefe's  test  indicates  that  the  eouvei-gence  is  relatively  weak — 
weak,  that  is,  as  compared  with  the  absolute  power  of  the  eye  to 
move  inward  (associated  adduction) .  But  whether  this  indicates  an 
absolute  weakness  of  convergence  or  not  depends  upon  whether  we 
regard  the  associated  adduction  (ability  of  the  eye  to  move  inward 
while  its  neighbor  moves  outward)  as  always  normally  less  than  the 
convergence  adduction  (ability  of  the  eye  to  move  inward  while  its 
neighbor  is  also  moving  inward).  Graefe  proceeds  upon  the  assump- 
tion that  this  is  the  case;  but  in  many  persons,  whom  I  examined 
and  who  had  apparently  normal  eyes,  the  associated  adduction 
seemed  the  greater  of  the  two.  In  such  the  fact  that  they  responded 
to  Graefe's  test  would  not  necessarily  indicate  the  existence  of  any- 
thing abnormal, 

As  to  its  nature,  convergence-insufficiency  may  be  either 
accommodative  or  non-accommodative.  Non  accommoda= 
tive  insufficiency  may  be  due  (A)  to  direct  weakness  of  the 
interni,  e.  rj.  that  obtaining  after  a  complete  tenotomy  of 
the  latter,  especially  when  the  operation  has  been  done 
upon  faulty  principles,  as  to  relieve  a  divergence -insuffi- 
ciency not  associated  with  excess  of  convergence.  This 
post-operative  weakness,  which  may  give  rise  to  a  very 
troublesome  asthenopia  lasting  for  several  months,  is,  to 
be  sure,  not  really  an  example  of  convergence-insufficiency, 
being  really  a  traumatic  paresis  of  the  interni,  but  in  its 
symptoms  and  course  it  so  much  resembles  the  former  as 
to  be  most  conveniently  considered  in  connection  with  it. 

Convergence -insufficiency  again  occurs  (B)  .secoiidrfrili/ 
to  a  direryeuce-excesK — this  being  an  example  of  that  com- 
pensatory action,  already  alluded  to,  by  virtue  of  which  a 
deviation,  which  is  at  first  marked  for  one  distance  only, 
tends  to  become  generalized  so  as  to  become  apparent  for 
all  distances  alike.  In  these  cases  there  is  at  first  a  marked 
exophoria  for  distance  accompanied  by  excessive  diverging 
power  (10  or  over),  but  with  only  moderate  exophoria  for 
near,  good  converging  power,  and  no  recession  of  the  near 


74  NEW  CLASSIFICATION  OF  MOTOR  ANOMALIES. 

point  of  convergence.  Later,  the  exophcria  for  near  in- 
creases markedly  (without  there  being  necessarily  any  in- 
crease in  the  exophoria  for  distance),  the  convergence 
near-point  recedes,  and  the  converging  power  gets  to  be 
performed  with  more  and  more  difficulty.  From  some  few 
observations  that  I  have  made  I  think  it  likely  that  this 
sort  of  extension  of  exophoria  may  occur  chiefly  in  young 
persons  as  a  result  of  the  processes  of  growth,  which,  as  is 
well  known,  favor  the  development  of  a  divergence  of  the 
visual  lines  and  which  may  abrogate  a  convergent  strabis- 
mus or  convert  a  case  of  parallelism  of  the  visual  axes  into 
one  of  divergent  squint. 

If  this  explanation  is  correct  these  cases  are  instances  of 
a  gradually  developing  bilateral  insufficiency  of  the  interni, 
rather  than  a  real  insufficiency  of  convergence. 

A  similar  explanation — viz.,  the  gradual  production  of 
an  anatomical  divergence  by  developmental  processes 
taking  place  during  the  period  of  growth — may  perhaps 
account  for  the  genesis  of  some  of  the  cases  of  convergence- 
insufficiency  not  complicated  with  a  divergence-excess. 

Another  variety  (C)  of  non-accommodative  convergence- 
insufficiency  appears  to  be  directly  dependent  upon  an 
iitsitfiriencii  of  an  elevator  or  depreeKor  muscle,  and  partic- 
ularly of  the  superior  rectus.  This  connection,  in  view  of 
the  assistance  that  these  vertically  acting  muscles  give  in 
effecting  adduction,  seems  not  unnatural  and,  at  all  events, 
appears  to  be  quite  frequent.  Thus  in  21  successive  cases 
occurring  in  my  practice  6  exhibited  marked  insufficiency, 
or  actual  paresis  of  the  vertical  muscles,  and  in  another 
series  of  27  that  I  examined  5  at  least  were  thus  affected. 

In  three  or  four  other  cases  there  was  more  or  less  weak- 
ness of  the  superior  and  inferior  recti  of  both  eyes,  caus- 
ing a  concentric  limitation  of  the  field  of  single  vision. 
This  weakness,  from  its  varying  character,  could  not  be 
regarded  as  due  to  paresis,  but  was  (D)  simply  one  of  the 
evidences  of  the  general  lack  of  inuscular  poicer  and  niKsca- 
lar  co-ordination  that  these  patients  presented.  Such  cases, 
therefore,  appear  to  occur  especially  in  neurasthenia. 
In  the  latter  condition,  at  any  rate,  and  in  allied  conditions 
of  general    enfeeblement,  convergence-insufficiency  is  of 


NEW  CLASSIFICATION  OP  MOTOR  ANOMALIES.  75 

frequent  occurrence  and  often  occasions  a  troublesome 
and  intractable  asthenopia  which  disappears  only  when 
the  causal  affection  has  been  removed. 

Accommodative  convergence=insufficiency  consists  in 
the  development  of  a  marked  divergence  for  near  points 
due  to  non-use  of  the  accommodation.  Accommo- 
dation being  usually  associated  with  convergence,  any 
condition  which  prevents  the  discharge  of  accommodative 
impulses  will  likewise  tend  to  inhibit  the  convergence. 
Theoretically  this  inhibition  should  occur  in  all  cases,  but 
practically  it  occurs  in  a  minority  only.  These  cases  may 
be  classified  as  follows : 

(a)  Patients  with  tiHcorrecfed  mi/opia ,  in  whom  there  is 
but  little  necessity  for  using  the  accommodation  at  all. 

(b)  In  Jniperinetropef:-,  who  having  all  along  accustomed 
themselves  to  using  their  accommodation  without  employ- 
ing a  corresponding  convergence  acquire  thereby  a  rel- 
ative insufficiency  of  the  latter  function,  which  comes  to 
light  as  soon  as  their  hypermetropia  is  corrected. 

Thus  a  mail  with  a  hypermetropia  of  2  D.  has  been  accustomed 
when  looking  at  an  object  13"  off  to  use  an  accommodation  of  5  D.; 
but  when  his  hypermetropia  is  corrected  by  glasses,  he  suddenlj- 
finds  that  at  this  distance  he  has  to  iise  only  3  D.  of  accommodation, 
an  amount  with  which  he  has  been  wont  to  associate  a  much  smaller 
degree  of  convergence.  Not  being  able  at  first  to  accustom  himself 
to  these  new  conditions,  /.  c.  not  l^eing  able  at  once  to  converge  to 
a  point  at  13"  witliout  using  5  D.,  his  visual  lines  diverge.  This  di- 
vergence often  gives  rise  to  considerable  trouble  (persistence  of 
asthenopia,  etc.)  and  constitutes  one  of  the  chief  reasons  why  con- 
vex glasses  are  not  tolerated  by  many  hypernietropes. 

For  a  similar  reason  convergence -insufficiency  may  de- 
velop (C)  in  in-e.sht/opes  who  first  put  on  convex  glasses  for 
near. 

The  marked  increase  in  a  convergence-insufficiency  gen- 
erally produced  by  (D)  the  continuous  use  of  2^nK»is, 
base  in,  is  also  probably  in  part  due  to  accommodative 
inaction;  the  use  of  such  glasses  by  favoring  divergence 
tending  to  relax  the  accommodation  still  more  and  hence 
to  superinduce  a  still  further  failure  of  the  convergence. 

The  rouvKeoi  a  convergence-insufficiency  varies  greatly. 
Many  cases,  particularly  those  dependent  upon  general 
muscular  and   nervous  weakness  remain  about  the  same 


76 


NEW  CLASSIFICATION  OF  MOTOR  ANOMALIES. 


for  a  long  time  and  then  improve  as  the  causal  condition 
improves.  Such  cases  may  also  show  recurrences,  when 
for  any  reason  there  is  a  new  deterioration  of  the  vital 
forces.  Cases  also  of  accommodative  convergence-insuffi- 
ciency due  to  a  readjustment  of  the  optical  conditions  under 
which  the  patient  has  been  working  (application  of  convex 
glasses  for  hypermetropia  and  presbyopia)  usually  get  well, 
the  patient  accustoming  himself  after  a  while  to  his  new 
refractive  state.  This  is,  however,  by  no  means  always 
the  case,  and,  if  a  tendency  to  convergence -insufficiency  al- 
ready exists,  it  may  become  aggravated  and  be  made  per- 
manent by  the  use  of  glasses— indeed,  the  development  of 
an  actual  strabismus  divergens  m^y  be  thus  superinduced, 
particularly  when  the  glass  chosen  for  a  hypermetropic 
child  has  been  somewhat  in  excess  of  the  true  hyper- 
metropia. 

Convergence -insufficiency  due  to  tenotomy  also  gener- 
ally tends  to  disappear,  although  this  again  cannot  be 
taken  as  the  invariable  rule. 

Other  cases  of  convergence-insufficiency,  and  partic- 
ularly those  occurring  in  young  persons  and  dependent 
upon  an  insufficiency  of  the  elevators  and  depressors,  tend 
to  increase.  This  seems  to  take  place  by  the  development 
of  a  divergence -excess  in  accordance  with  the  law  of 
compensation  already  several  times  referred  to,  by  which 
a  non-comitant  deviation  tends  to  become  comitant.  The 
course  of  such  cases,  if  unchecked,  is  first  increase  of 
the  exophoria  for  near,  second  development  of  exophoria 
for  distance  also,  with  increased  diverging  power  (Di- 
vergence excess),  next  the  appearance  of  an  actual  diver- 
gent strabismus  for  near  with  considerable  exophoria  for 
distance  (Periodic  squint),  and  finally  divergent  strabis- 
mus for  both  distance  and  near  (Constant  squint) .  This  ten- 
dency to  a  constantly  increasing  divergence  may  be  favored 
by  the  injudicious  use  of  convex  glasses  and  particularly  by 
the  use  of  prisms  base  in,  which  almost  always  tend  to 
make  the  exophoria  greater  and  greater.* 

*I  observed  one  marked  case  of  this  sort,  occiirrinsr  in  a  Kirl  of  nine,  who  at  first 
had  3"^  of  exophoria  for  distance  and  over  6°  for  near,  but  wlio  after  iisinjr  prisms  for 
a  year  had  for  distance  exophoria  of  .S"  with  abduction  of  lO'^-lJ"  and  spontaneous 
crossed  dii)lopia.  aiul  for  near  exophoria  of  15°.     rrism-couverEeiice   (adduction)  0^. 


NEW  CLASSIFICATION  OF  MOTOR  ANOMALIES.  77 

As  has  been  seen,  convergence-insufficiency  may  be 
compHrafed  with  an  insufficiency  of  one  of  the  vertical 
muscles,  the  latter  affection,  indeed,  in  these  cases  prob- 
ably being  the  cause  of  the  former.  In  other  cases,  a  di- 
vergence-excess is  present  which  ie  sometimes  the 
cause,  but  more  often  the  effect,  of  the  convergence-insuf- 
ficiency. The  latter  may  also,  particularly  in  those  whose 
muscular  system  generally  is  weak,  be  complicated  with  a 
divergence-insufficiency.*  Slight  cases  of  this  sort,  in 
which  the  insufficiency  of  divergence  is  not  great 
enough  to  produce  esophoria  for  distance  constitute  the 
asthenic  exophoria  of  Savage. 

The  si/mjjfom.sot  convergence-insufficiency  are  astheno- 
pia, either  simple,  or  associated  with  headache  and  pain  in 
the  eyes,  conjunctival  irritation,  and  spontaneous  diplopia, 
producing  blurring  of  vision  for  near  work.  Asthenopia  is 
a  pretty  constant  symptom,  being  met  with  in  all  the  va- 
rieties, although  in  my  experience  more  apt  to  occur  in  the 
non -accommodative  than  in  the  accommodative  form.  It 
is  often  very  marked  and  may  incapacitate  the  patient  from 
doing  near  work. 

The  symptoms  are  by  no  means  necessarily  in  direct  re- 
lation with  the  amount  of  the  deviation,  being,  in  fact, 
more  pronounced  in  deviation  of  medium  degree  than  in 
those  which  have  assumed  the  proportions  of  a  regular 
squint. 

It  is  for  this  reason,  probably,  that  the  use  of  concave  glasses  in 
myopes  affected  with  convergence-insufficiency  sometimes  causes 
distress;  since  these  glasses  tend  to  increase  the  impulse  to  converg- 
ence and  thus  rediiee  a  large  deviation,  which  is  insuperable  and 
gives  no  trouble,  to  a  smaller  one  which  can  be  overcome  by  effort 
and  hence  gives  more  annoyance.  On  the  other  hand,  Avhen  the  de- 
viation is  very  small  to  begin  with,  the  symptoms  may  be  aggravated 
by  the  use  of  convex  glasses  and  of  prisms  base  in,  which  tend  to 
make  it  larger  and  therefore  more  troublesome. 

The  treatment  of  convergence-insufficiency  must  aim 
first  at  removing  the  cause  of  the  trouble.     Hence  in  neu- 

By  exercise  of  the  convergence  with  prisms  the  exophoria  for  distance  was  reduced 
to  0°-3°,  that  for  near  to  5°-6°,  the  prisni-converRence  was  raised  to  40°-50°,  and  there 
was  no  more  spontaneous  diplopia.  This  improvement  was  maintained  up  to  the 
time  that  the  patient  was  last  seen  (7  months  after  the  treatment  had  been  discon- 
tinued). 

*I  liave  notes  of  a  case  of  this  sort  in  a  myope  of  8-10  D.,  in  whom  there  was  an 
esophoria  of  14-20°  (i.  e.  a  real  convergent  squint)  for  distance,  with  diverging  power 
of  2-3°,  and  exophoria  of  8°  for  near. 


78  NEW  CLASSIFICATION  OF  MOTOR  ANOMALIES. 

rasthenia  general  strengthening  measures  (out-of-door 
exercise,  tonics)  are  indicated  and  are  for  the  most  part 
successful.  Accommodative  convergence  -  insufficiency 
requires  the  careful  correction  of  the  refraction  in  myopia, 
while  in  hypermetropia  frequently  an  under-correction  will 
be  indicated.  Indeed,  it  is  a  safe  general  rule  to  fully  cor- 
rect myopia  and  to  under-correct  hypermetropia  whenever 
much  exophoria  exists;  and  in  presbyopia  under  the  same 
conditions  to  give  a  weaker  convex  glass  than  would  other- 
wise seem  indicated. 

The  immediate  causal  indication  requires  trahuiKj  oftha 
convergence,  which  can,  in  general,  be  effected  by  system- 
atic exercise  with  prisms  base  out.  This  often  gives  strik- 
ingly good  results,  but  in  some  cases  fails  altogether. 

The  wearing  of  prisnix  base  in  should  be  resorted  to  only 
as  a  temporary  expedient,  on  account  of  their  tendency  to 
produce  increase  of  the  trouble;  and  these  prisms  should 
be  discontinued  at  once  as  soon  as  signs  of  such  an  in- 
crease begin  to  manifest  themselves. 

Finally,  if  an  ojwration  is  decided  upon,  advancement  of 
the  interni,  coupled,  in  case  a  divergence-excess  is  pres- 
ent, with  a  tenotomy  of  the  externi,  should  be  made.  Te- 
notomy of  the  externi  alone  seldom  gives  any  lasting  re- 
sult. 

Hyperklneses.  5pasm  and  Excess  of  Convergence. 
Marked  tonic  spasm  of  convergence,  so  that  both  eyes  are 
turned  strongly  inward,  has  been  observed  in  hysteria. 

Minor  degrees  of  over-action  of  convergence  (Converg- 
ence=excess)  are  of  frequent  occurrence.  They  may  be 
either  accommodative  or  non-accommodative  in  character. 

lYie  ijhysical  siffnx  oi  a  convergence- excess  not  compli- 
cated with  a  divergence-insufficiency  are  as  follows: 

For  distance.  Orthophoria  or  moderate  esophoria  ( 1  -3  ) 
by  all  tests  (phorometer,  screen  and  parallax).  Associ- 
ated lateral  movements  normal.  Diverging  power  normal 
or  but  slightly  subnormal  (S^'-S^).  Prism-convergence 
(adduction)  normal  in  amount,  rapidly  acquired,  and  easy 
to  produce  and  maintain.  Exercise  of  convergence  not 
infrequently  causing  the  development  of  temporary  homo- 


NEW  CLASSIFICATION  OF  MOTOR  ANOMALIES.  79 

nymous  diplopia.  Homonymous  diplopia  sometimes  also 
producible  by  will  and  apparently  without  effort. 

For  near.  Esophoria  by  all  tests,  often  exceeding  that 
for  distance.*     Convergence  near-point  li"-l"  or  less. 

Non=accommodative  convergence=excess  may  be  either 
(a)  idiopathic  or  may  (b)  be  secondary  to  a  condition  of 
divergence-insufficiency.  The  former  appears  to  be  rare, 
although  I  have  met  with  two  or  three  cases.  The  second- 
ary variety,  on  the  other  hand,  appears  to  be  quite  com- 
mon, and  develops  according  to  the  compensatory  law  by 
which  deviations  in  general,  tend  to  become  equalized  for 
distance  and  near.  In  this  case,  of  course,  there  will  be 
marked  esophoria  for  distance  and  the  diverging  power 
(abduction)  will  be  much  reduced. 

Non-accommodative  convergence-excess  probably  com- 
prises most  of  the  cases  described  by  Savage  under  the 
name  of  sthenic  esophoria. 

Accommodative  convergence  =  excess  (Accommodative 
esophoria,  Accommodative  convergent  squint,  Pseudo- eso- 
phoria) is  very  frequent.  It  occurs  under  the  following 
conditions : 

(a)  Uncorrected  Jiyperhtefropia.  The  effect  of  this  in 
producing  inward  deviation  of  all  degrees  from  a  slight  eso- 
phoria to  a  marked  strabismus  is  too  well  known  to  require 
further  comment  here. 

(b)  In  iiii/ojjes  who  for  the  first  time  use  a  concave  glass 
for  near  points.  Such  patients  will  add  to  the  natural 
amount  of  convergence  for  the  point  they  are  looking  at 
(which  convergence  they  have  hitherto  been  accustomed  to 
make  without  using  any  accommodation)  the  extra  conver- 
gence imposed  in  sympathy  with  the  accommodative  effort 
that  they  now  make  for  the  first  time. 

(c)  In  presbt/opes  (particularly,  hyperopic  presbyopes) 
at  the  beginning  of  the  presbyopic  period.  These  patients 
have  to  exert  a  very  strong  effort  in  order  to  stimulate  their 
flagging  accommodation  to  the  point  necessary  for  distinct 

*Unless,  however,  the  patient  really  fixes  upon  the  test  object,  the  esophoria  for 
near  may  vary  greatly  and  even  be  replaced  temporarily  by  exophoria.  This  is  par- 
ticularly apt  to  be  the  case  in  accommodative  convergrence-excess,  where  the  amount 
of  hypermetropia  may  ce  such  as  to  prevent  the  patient  from  seeing  the  object  dis- 
tinctly. 


80  NEW  CLASSIFICATION  OF  MOTOR  ANOMALIES. 

vision,  and  in  sympathy  with  this  excessive  call  made  upon 
the  accommodation  an  excessive  effort  of  convergence  is 
simultaneously  made. 

(d)  Af<  the  rei^nlt  of  thf  instillntioti  of  a  ynydriatic.  The 
increase  of  a  convergent  squint  by  the  instillation  of  atro- 
pine was  observed  by  Long  and  Barrett  (Ophth.  Hosp.  Re- 
ports, xii.  1888-1889),  who  found  that  it  occurred  in  11 
cases  out  of  38  in  whom  this  mydriatic  was  employed. 
These  cases,  however,  had  been  under  the  influence  of  the 
atropine  for  several  days.  In  cases  which  are  but  recently 
under  the  influence  of  the  mydriatic  an  increased  tendency 
to  convergence  due  to  the  latter  appears  to  be  even  more 
frequent.  Under  these  circumstances  esophoria  may  de- 
velop where  orthophoria  existed  before,  and  a  pre-existing 
esophoria  of  moderate  amount  may  develop  into  a  well- 
marked  convergent  squint. 

The  t'orrect  explanation  of  this  phenomenon  was  first  g'iven  by 
Savaj^e,  althougli  I  myself  came  independently  to  the  same  conclu- 
sion. The  converg'ence  here  is  evidently  due  to  the  excessive  effort 
which  the  patient  makes  to  see  distinctly  under  the  unusual  condi- 
tions presented  by  mydriasis.  Not  bein^  aware  that  he  cannot  accom- 
modate, he  makes  a  violent  effort  to  do  so,  and  in  making  this  effort 
sends  out  a  correspondingly  strong  impulse  for  convergence.  The  cili- 
ary muscle  does  not  respond,  but  the  interni  do;  and,  as  the  impulse 
was  excessive,  they  I'espond  by  producing  an  excessive  convergence. 
The  condition,  in  fact,  is  quite  analogous  to  the  excessive  secondary 
deviation  of  the  sound  eye  when  its  fellow  attempts  to  perform  fixa- 
tion by  means  of  a  paralyzed  nniscle. 

As  under  the  mydriatic  the  sight  is  more  blurred  for  near 
than  for  distance,  this  fruitless  effort  to  see  distinctly  by 
attempting  to  put  into  motion  a  paralyzed  accommodation 
will  be  more  excessive,  and  hence  too  the  esophoria  will  be 
more  pronounced,  for  near  points.  For  distance,  the  eso- 
phoria will  generally  be  greater  in  proportion  to  the  degree 
of  hypermetropia  and  the  consequent  blurring  of  sight,  and 
will  often  disappear  altogether  as  soon  as  the  refraction  is 
corrected.     These  facts  are  shown  in  the  following  cases: 

EsopHoKiA.  Lakhk  ixcrkask  undkr  mydriatic.  Miss  K.,  aged 
20.  Refraction  (under  homatropine)  -f-  0.2.')  sph.  O  -f  O.'iO  cyl.  ax. 
V,  each.  When  not  under  mydriatic  shows  esophoria  '-^1°  for  both 
distance  and  near  (with  and  without  correction  of  refraction):  di- 
verging power,  (»'  I'lider  liomatropine,  witli<»ut  correction  of  refrac- 
tion. (■s()i)lioriM    for   distance   over   S".  for   near  over    1.")"^.   diverging 


NEW  CLASSIFICATION  OF  MOTOR  ANOMALIES.  81 

power  8°.     I'lidcr  lioniatropinc,  witli   conrctioii   of  rt'fraotion,  t-so- 
phoria  for  distance  ;")',  for  near  over  1')". 

2.  J.  B.,  male,  aged  15.  Hypernietropia  (lioniatropine)  O.-OU  1). 
Before  homatropine,  esophoria  3°  for  distance,  ()'  for  near.  Under 
lioniatropine,  (witli  and  without  correction  of  refraction),  2'/-.'°  for 
distance,  7°  for  near.     Diverging  power  4°. 

3.  Kath.  S.,  aged  32.  Hypernietropia  2.2;il)  (under  homatropine). 
Before  homatropine,  esophoria  2°-^°  for  distance,  1°  for  near;  di- 
verging power  5°.  Under  homatropine,  without  correction  of  refrac- 
tion, 12''-20°  for  distance,  12°  for  near  (i.  e.  has  an  actual  convergent 
squint).  Under  homatropine  and  with  correction  of  refraction,  eso- 
phoria '/j°  for  distance;  little,  if  any  for  near. 

The  course  in  case  of  convergence-excess  is  very  vari- 
able. The  accommodative  variety,  in  particular,  often 
decreases  or  disappears  spontaneously  either  as  a  result 
of  developmental  changes,  favoring  the  genesis  of  a  diver- 
gence, or  in  consequence  of  the  decrease  of  the  hyperme- 
tropia,  or  because  the  patient  gives  up  the  accommodative 
effort  and  with  it  the  effort  to  converge.  Its  usually  speedy 
and  total  disappearance  in  cases  coming  under  cate- 
gories B,  C,  and  D  above  given,  is  to  be  ascribed  to  the 
last  mentioned  cause. 

In  other  cases,  particularly  in  the  very  young  who  are 
beginning  to  tax  their  accommodation  more  and  more  with 
school  work,  the  deviation  increases ;  the  regular  course 
being,  first,  increase  of  the  esophoria  for  near,  then 
increase  of  the  esophoria  for  distance  with  reduction  of  the 
diverging  power  (Development  of  divergence-insuffici- 
ency), next  the  development  of  an  absolute  squint  for 
near  points  where  accommodative  effort  is  most  required 
(Periodic  squint) ,  and  lastly  strabismus  convergens  marked 
for  both  distant  and  near  (Constant  squint).  A  squint 
when  thus  fully  developed  usually  remains  permanently, 
but  may  disappear  in  latter  life  through  the  agencies 
mentioned  in  the  preceding  paragraph. 

As  already  noted,  convergence -excess  may  be  coinjili- 
cated  with  divergence-insufficiency,  the  latter  condition 
being  either  the  cause  or  the  effect  of  the  former.  It  is 
also  frequently  complicated  with  some  form  of  vertical  de- 
viation, producing  hyperphoria  in  addition  to  the  esopho- 
ria.    It  seems,  in  fact,  not  unlikely  that  these  vertical  de- 


82  NEW  CLASSIFICATION  OF  MOTOR  ANOMALIES. 

viations  play  an  important  part  in  the  genesis  of  the 
excessive  tendency  to  convergence. 

The  si/iNp/oh/s  of  convergence -excess  are  asthenopia, 
headache,  and  spontaneous  homonymous  diplopia,  with 
sometimes  more  marked  reflex  disturbances.  These  symp- 
toms, however,  are  much  less  pronounced  and  constant 
than  in  cases  either  of  convergence-insufficiency  or  diver- 
gence-insufficiency, and  when  present  are  usually  due  to 
the  attendant  hypermetropia  or,  at  least,  disappear  when 
the  latter  is  corrected. 

The  treafiiienf  of  convergence-excess  is  largely  causal, 
consisting  particularly  in  the  correction  of  the  refraction. 
In  doing  this  we  shall  do  well  to  follow  the  rule  that  when 
there  is  marked  esophoria  and,  particularly,  when  there  is 
more  esophoria  for  near  than  for  distance,  we  must  fully 
correct  any  hypermetropia  and,  on  the  other  hand,  under- 
correct  any  myopia,  that  may  be  present. 

The  result  of  treatment,  both  as  regards  the  removal  of 
the  deviation  and  the  relief  of  the  symptoms  are  very 
good.  Even  in  well-marked  convergent  squint  a  cure  is 
effected  much  oftener  than  is  generally  supposed,  the 
only  requisites  being  that  the  refractive  treatment  should 
be  kept  up  long  enough  (a  year  at  least)"*  Long  and 
Barrett  (1.  c.)  analyzing  the  results  in  102  cases,  found 
that  a  complete  cure  was  effected  in  37,  while  out  of  61 
cases  under  10  years  of  age  27  (or  44  per  cent.)  were  cured. 

In  addition  to  correcting  the  refraction  we  may  try  to 
break  up  the  excessive  tendency  to  convergence  by  aool- 
ishing  the  accommodation  altogether  for  a  time.  This  we 
effect  by  keeping  the  eyes  under  afropine  for  a  number  of 
days  or  even  several  weeks.  This  may  also,  if  Long  and 
Barrett's  figures  hold  good  generally,  be  used  as  a  means 
of  prognosis,  for  these  authors  found  that  of  5  cases  which 
were  improved  by  atropine  all  were  subsequently  improved 
by  glasses,  while  of  6,  in  whom  the  deviation  was  not 
affected  by  the  atropine,  only  3,  and  of  4,  in  whom  the 
atropine  made  the  convergence  worse,  only  1  received  any 
relief  from  the  correction  of  their  refraction. 

*This,  becomes  the  coiiliinioiis  relaxation  of  the  interiii  thus  pioiliKid  allows  the 
weakened  extenii  to  act  to  Ri eater  ad v:inta);e  aiul  finally  to  regain  tlieir  tone  (UonK 
and  Harretl). 


NEW  CLASSIFICATION  OF  MOTOR  ANOMALIES.  83 

Exercise  of  the  divergence  with  jtris/ns  is  of  no  service 
in  this  condition,  and  the  wearing  of  prisms  base  out  is  to 
be  deprecated  as  tending  to  perpetuate  and  increase  the 
deviation  instead  of  curing  it. 

If  these  means  fail  and  an  opera f ion  is  thought  advioable 
on  account  of  the  deformity  or  the  symptoms,  tenotomy  of 
the  interni  may  be  done,  combined,  in  case  a  divergence- 
insufficiency  is  present,  with  an  advancement  of  the  ex- 
terni. 


VIII. 
ANOMALIES  OF  DIVERGENCE. 

Hypokinesis.  Divergence=Insufficiency.  Weakness  of 
the  diverging  power  (Divergence-Insufficiency)is  charac- 
terized by  the  following  signs : 

F'or  Distance. — Esophoria  of  varying  amount  (usually 
2''-8'^),  by  all  tests  (phorometer,  screen,  and  parallax). 
Associated  lateral  movements  normal.  Diverging  power 
very  much  reduced,  the  reduction  being  often  proportion- 
ate to  the  degree  of  the  esophoria  (  e.  g.,  with  an  esophoria 
of  3"  or  4°,  the  diverging  power  is  about  4",  and  with  an 
esophoria  of  5°  or  6°,  the  diverging  power  is  only  2°) .  In 
the  typical  cases  of  this  anomaly,  however,  the  diverging 
power  is  disproportionately  low,  being,  for  example,  only 
2°  or  3°,  when  the  esophoria  is  1°  or  2"',  and  being,  perhaps, 
only  3°  or  4°  when  there  is  orthophoria  or  actual  exophoria 
for  distance.  Exercise  of  divergence  with  prisms,  base  in, 
is  sometimes  associated  with  a  sense  of  decided  muscular 
strain. 

Prism-convergence  (adduction)  normal,  or  often  some- 
what deficient.  Exercise  of  the  convergence  often  gives 
rise  to  a  temporary  homonymous  diplopia,  and  the  latter 
may  also  in  some  cases  (particularly  when  the  diverging 
power  is  much  reduced)  occur  spontaneously,  or  be 
evoked  by  simply  placing  a  red  glass  before  one  eye. 

For  year. — Signs,  unless  the  condition  is  associated 
with  a  convergence-insufficiency,  or  with  a  convergence- 
excess,  fairly  normal  (  /.  e.,  slight  esophoria  or  exophoria, 


84  NEW  CLASSIFICATION  OF  MOTOR  ANOMALIES. 

and  convergence  near-point  at  about  the  proper  distance). 

In  its  orii/in  divergence- insufficiency  is  either  idiopathic 
or  secondary  to  a  convergence-excess. 

Uncomplicated  i<li<>i><ttliic  divergence-insufficiency  is 
comparatively  rare,  and,  moreover,  some  of  the  cases  that 
would  seem  to  fall  in  this  category  are  probably  either 
really  secondary  to  some  disorder  of  the  vertical  muscles 
(elevators  or  depressors),  or  are  examples  of  a  spurious 
divergence-insufficiency,  /.  r.,  of  a  condition  in  which 
there  is  actual  weakness  of  the  externi  themselves,  either 
natural  or  produced  by  operation.  In  cases  of  the  latter 
kind  the  divergence  is  indeed  weak,  but  the  power  of  mak- 
ing lateral  movements  is  also  lessened,  and  hence  these 
cases  do  not  fairly  come  under  the  head  of  a  simple  im- 
pairment of  the  diverging  function. 

Complicated  idiopathic  divergence-insufficiency  is  more 
common.  In  these  cases  there  is  either  a  convergence- 
insufficiency,  which  has  developed  simultaneously  with  the 
disorder  of  divergence,  or  there  is  a  convergence- excess, 
which  is  the  result  of  the  latter. 

SeroiKhtri/  <lii'('i'{ieiK'e-hisnfficietic;i  develops  in  the  man- 
ner already  described  (see  Section  VII.)  from  a  progress- 
ively increasing  convergence-excess.  Cases  of  this  sort 
might  be  confounded  with  those  of  the  foregoing  category, 
/.  f.,  those  in  which  a  primary  divergence-insufficiency  is 
followed  by  excessive  convergence  action.  The  distinc- 
tive points  between  the  two  may  be  stated  as  follows: 


PRIMARY  I)IVKR(iEXCK  -  INSUFFI 
CIKNCY.  WITH  SECONDARY  CON- 
VKRCiKNCK-EXCESS. 

Ks()i)li()ria  for  distancf   nioder- 


PRIMARY      CON YER(4EX<  E-EXCESS . 
WITH    SECONDARY  DIYEJiGENCE- 
INSUFFKTENCY. 
Esoplioj-ia   for    (listaiicc   often 


ate  (not  ovc'i-  S'').aii(lniaybe  less      jrreat,    and    when    small    usnallx 
than  tlitMh'liciency  ititlie  divei-.u--   I  disi)roi)ort  ionately  larue    in   coin- 


injj-  jxnver   (aliilnction  ). 

Ksoi)horia  f<.r  iieai-  small  and 
usually  less  than  that  for  dis- 
tance. 

( 'ondition  stationai-v. 


parison  with  the  delieiem-y  of  di- 
veryiii^-  power. 

Ksophoria  for  near  usnally 
greater  tliaii  for  distance. 

( 'ondition  ofl<'n  ])ro^n-essive. 

The  ro///-.s7  pursued  by  a  divergence-insufficiency  is  in- 
dicated in  what  has  already  been  said.  The  idiopathic 
variety  shows  l>ut  iitth"  tondoncy  to  change,  the  amount  of 


NEW  CLASSIFICATION  OF  MOTOR  ANOMALIES.  85 

esophoria  and  of  divergence-weakness  often  remaining  the 
same  for  years.  This  variety  frequently  becomes  compli- 
cated with  a  condition  of  convergence-excess,  which,  how- 
3ver,  also  remains  of  moderate  degree.  On  the  other  hand, 
a  divergence-insufficiency,  which  is  secondary  to  a  con- 
vergence-excess, is  often  progressive,  the  advance  contin- 
uing in  many  cases  until  a  moderate  deviation  is  converted 
into  a  marked  and  constant  strabismus  convergens. 

The  si/)i/j)/oins  of  a  divergence-insufficiency  are  often 
very  troublesome.  Asthenopia  as  a  result  of  near  work  is 
not  so  much  complained  of,  unless  there  is  a  simultaneous 
convergence-insufficiency,  but  headache  and  other  more 
remote  reflex  pains,  a  sense  of  constriction  in  the  head, 
stomach  disturbance,  general  inertness  and  lassitude,  and 
even  interference  with  the  general  nutrition  are  often  met 
with.  Spontaneous  diplopia  may  also  occur,  being,  nat- 
urally, more  marked  for  distance  than  for  near.  One 
peculiarity  in  the  symptoms  is  that  headache  and  pro- 
nounced asthenopic  sensations  (feeling  of  strain  and 
tiring  in  the  eyes) ,  together  with  a  sense  of  confusion  and 
dullness  in  the  head,  are  especially  apt  to  be  produced  by 
looking  long  and  intently  at  distant  objects,  particularly 
when  moving  or  when  brightly  illuminated.  Such  symp- 
toms are  hence  often  occasioned  by  watching  a  theatrical 
performance,  a  ball-match,  a  procession,  or  a  moving 
throng  of  people.  (Panorama-asthenopia,  or  panorama- 
headache  of  Bennett.)* 

The  freafment  of  divergence-insufficiency  presents  many 
difficulties,  the  condition  being  intractable  and  the  result 
uncertain. 

Direct  exercise  of  the  divergence  with  prisms,  base  in, 
has  not,  in  my  experience,  been  of  the  least  avail.  Exer- 
cise by  the  performance  of  systematic  lateral  movements 
of  the  eyes  seems  unphysiological,  inasmuch  as  it  is  the 
externi  that  are  thus  practiced,  and  not  the  function  of  di- 
vergence per  !<(^,  and,  moreover,  in  these  movements  the 
interni  are  practiced  along  with  the  externi.  Some,  how- 
ever, seem  to  have  obtained  good  results  by  this  method. 

The  constant  wearing  of  prisms,   base  out,  is  in  most 

*Annals  of  Ophthalmology,  January,  1897. 


86  NEW  CLASSIFICATION  OF  MOTOR  ANOMALIES. 

cases  a  dangerous  expedient,  as  tending  to  cause  disuse 
and  a  consequent  further  enfeeblement  of  the  abducting 
power. 

If  an  operation  is  resorted  to,  it  should,  in  the  idiopathic 
cases  at  all  events,  be  an  advancement  of  the  externi 
rather  than  a  tenotomy  of  the  interni.  The  latter  opera- 
tion by  itself  is  almost  always  nugatory,  the  condition 
tending,  after  a  temporary  period  of  improvement,  to  re- 
turn to  its  original  state.  Moreover,  the  tenotomy,  if 
thorough  enough  to  be  efficacious,  is  liable  to  substitute  for 
the  unpleasant  asthenopia  for  distance  an  almost  equally 
annoying  asthenopia  for  near.  In  the  secondary  cases, 
however,  or  wherever  a  marked  convergence-excess  is 
present,  tenotomy  of  the  interni  may  be  performed;  but 
even  then  it  is  preferably  combined  with  advancement  of 
the  externi. 

Hyperkinesis.  Divergence=Excess.  Over-action  of  di- 
vergence (iJirt'nitiKu^-E.i'crss)  is  marked  by  the  following 
signs : 

For  dhtance.  Exophoria,  usually  marked  (from  4  up- 
ward) with  noticeable  deviation  out  behind  the  screen. 
Associated  lateral  movements  normal.  Diverging  power 
excessive  (over  9"),  the  excess  over  the  normal  amount  of 
6"  or  8^  being  often  roughly  proportioned  to  the  degree  of 
the  exophoria,  but  sometimes  being  disproportionately 
larger.  Prism-convergence  (adduction)  in  uncomplicated 
cases  normal,  although  possibly  performed  with  difficulty 
at  first.  Crossed  diplopia  for  distance  often  occurring 
spontaneously,  or  producible  at  will. 

For  vcar.  Conditions,  unless  a  convergence-insuf- 
ficiency also  exists,  fairly  normal  (/.  (\,  exophoria  less,  or, 
at  all  events,  not  much  greater,  than  for  distance,  and  near 
point  of  convergence  about  in  its  normal  situation). 

A  divergence-excess  may  either  be  primary  in  or/'oiu  or 
be  secondary  to  a  convergence-insufficiency. 

/'riiiiffrt/  divergence-excess  occurs  not  infrequently  as 
an  uncomplicated  affection,  but  still  more  often  is  asso- 
ciated with  a  vertical  deviation  (which  may  really  stand 
in  genetic  relation  with  it),  .)i'  with  n  consecutive  convcrg- 


NEW  CLASSIFICATION  OF  MOTOR  ANOMALIES.  87 

ence-insufficiency,  It  may  also  be  associated  with  a 
convergence-excess.  I  have  observed  several  instances  of 
this  latter  combination,  in  which, with  exophoria  for  distance 
and  a  high  diverging  power,  there  was  also  excessive  power 
of  convergence,  and  either  actual  esophoria  for  near,  or  at 
least  an  exophoria  slight  in  amount,  and  much  less  than 
that  for  distance. 

The  development  of  a  st^roiidarn  divergence-excess  from 
a  convergence-insufficiency  has  already  been  traced  (see 
Section  VIII).  These  cases,  like  the  simple  ones  of  con- 
vergence-insufficiency which  represent  only  a  less  ad- 
vanced stage  of  the  same  process,  often  show  complicating 
insufficiency  of  the  vertical  muscles.  Indeed,  as  before  re- 
marked, this  last-named  condition  would  seem  to  consti- 
tute the  real  cause  of  the  divergence  which  takes  place, 
first  for  near  and  then  for  distance. 

The  differential  points  between  a  primary  divergence - 
excess  with  a  secondary  convergence -insufficiency  and  a 
primary,  convergence-insufficiency  with  consecutive  di- 
vergence-excess are  as  follows: 

PRIMARY  mVERGENCE  -  EXCESS  I  PRIMARY  CONVERGENCE-INSUFFI- 
WITHSE:!0NDARY  CONVERGENCE-  |  CIENCY  WITH  SECONDARY  Dl- 
INSUFPICIENCY.  |         VERGENCE-EXCESS. 

Exophoria  about  equal  for  dis-  Exophoria  for  near  much  great- 

tance  aud  near.  er  than  for  distance. 

Converging  power  and  prism-  Convergnig  power  greatly  at- 

convergence  not  excessively  af-  fected. 
fected. 

Recession  of  convergence  near-  Recession  ot  convergence  near- 
point  moderate.  point  marked. 

Condition  shows  little  tendency  Often  markedly  progressive, 
to  progress. 

As  above  stated,  cases  of  primary  divergence-excess 
show  but  little  tendency  to  progress.  I  have  had  one 
such  case  under  observation  for  over  nine  years,  in  which 
the  divergence,  although  large,  has  shown  but  moderate 
fluctuations — indeed,  may  be  said  to  have  remained  prac- 
tically unchanged— during  the  whole  time.  Cases,  on  the 
other  hand,  of  secondary  divergence-excess  are  often  prog- 
gressive,  a  moderate  degree  of  exophoria  developing 
gradually  into  a  marked  divergent  squint. 

The  si/ijipfoii/s  presented  by  a  case  of  divergence -excess 
are  frequently  slight.    The  most  troublesome  are  those  due 


88  NEW  CLASSIFICATION  OF  MOTOR  ANOMALIES. 

to  an  associated  convergence-insufficiency,  and,  if  this  is 
absent,  the  patient  may  complain  of  nothing  except  possi- 
bly of  a  spontaneously  occurring  crossed  diplopia  for  dis- 
tance, or  of  the  deformity  occasioned  by  the  noticeable  de- 
viation of  the  eyes.  Headache  and  asthenopia  may,  how- 
ever, also  occur. 

The  firaftneiif  of  a  divergence-excess  will  be  addressed 
mainly  to  the  correction  of  the  refraction  and  to  the  relief 
of  an  associated  convergence-insufficiency.  If  an  opera- 
tion is  performed,  tenotomy  of  the  externi  may  be  done; 
but  it  will  often  have  to  be  supplemented  by  systematic 
exercise  of  the  convergence  and  even  by  advancement  of 
the  interni. 

IX. 

ANOMALIES  OF  SURSUMVERGENCE. 

Hypokinesis.     Sursumvergence=lnsufficiency.     It  is  not 

certain  whether  sursumvergence,  /.  c,  the  separation  of 
the  visual  lines  in  a  vertical  plane,  is  ever  performed  by 
the  eyes  in  the  execution  of  normal  movements.  It  seems, 
however,  likely  that  some  such  action  may  be  serviceable 
incidentally  in  the  act  of  elevating  or  depressing  the  eyes. 
If  so,  great  impairment  of  the  sursumvergence  would  con- 
stitute a  serious  deficiency.  As  far  as  I  have  seen,  how- 
ever, limitation  of  sursumvergence  appears  to  have  no 
special  injurious  effect. 

Those  who  regard  the  amount  of  sursumvergence  as  a 
measure  of  the  strength  of  the  elevators  and  depressors 
(which  it  surely  is  not)  lay  more  stress  than  I  have  done 
on  the  limitation  of  this  function,  and  recommend  system- 
atic exercise  of  the  latter  by  means  of  prisms,  base  up  or 
down,  in  cases  where  it  is  subnormal.  I  have  had  some 
experience  with  these  methods,  but  not  enough  to  enable 
me  to  speak  with  assurance  as  to  their  value.  My  results, 
such  as  they  were,  have  not  led  me  to  expect  much  from 
training  of  this  sort. 

Hyperkinesis.  Sursumvergence-Excess.  Excessive  power 
of  sursumvergence   is   observed  in  many  patients  affected 


NEW  CLASSIFICATION  OF  MOTOR  ANOMALIES.  89 

with  hyperphoria  and  particularly  in  myopes  who  have  an 
artificial  hyperphoria  from  wearing  ill-fitting  concave 
glasses.  The  latter,  as  they  shift  in  various  positions, 
produce  prismatic  effects  changing  in  degree  and  in  direc- 
tion, and  hence  requiring  a  variable  effort  to  overcome  the 
diplopia  to  which  they  would  naturally  give  rise.  This 
constant  exercise  gives  rise  often  to  a  considerable  in- 
crease in  the  power  of  sursumvergence,  the  latter  some- 
times attaining  10°  or  more. 

A  true  su rsK Nifergenre-excess,  i.  e.,  a  state  of  habitual 
divergence  of  the  visual  lines  in  a  vertical  plane,  due  to 
excess  of  sursumvergence  action,  constitutes  one  of  the 
varieties  of  hyperphoria,  and  probably  accounts  for  some 
of  the  cases  of  strabismus  sursumvergens  and  strabismus 
deorsumvergens.  These  cases  must  not  be  confounded 
with  a  similar  vertical  deviation  due  to  paresis  or  insuf- 
ficiency of  some  of  the  individual  muscles.  The  differen- 
tial diagnosis  between  the  two  will  be  established  by  mak- 
ing the  screen  and  diplopia  tests  in  different  portions  of 
the  field  of  fixation,  when,  if  there  is  an  insufficiency  of 
any  individual  muscle,  a  deviation  or  a  diplopia,  showing  a 
characteristic  increase  in  some  one  direction  of  the  gaze, 
will  be  found  to  exist  (see  Section  VI). 

In  sursumvergence-excess  either  the  right  or  the  left 
visual  line  may  be  habitually  higher  than  the  other  (  r'Kjltt 
and  left  Jiyperphoria ),  or  each  alternately  may  be  higher 
(alternating  liuperphoria).  If  the  deviation  is  considera- 
ble and  not  habitually  overcome,  the  condition  is  known 
as  a  vertical  squint  (ht/pertropia  ),  which  again  is  called 
right  or  left  hypertropia,  according  as  the  right  or  the  left 
visual  line  is  above.  Vertical  squint  is  also  classified  into 
strabisinus  sursumvergens  when  the  lower  eye  is  the  one 
that  habitually  fixes,  and  strahisiitus  deorstiinvergens  when 
the  upper  is  the  fixing  and  the  lower  the  non-fixing  eye. 

Regularly,  in  such  cases,  the  deflection  follows  the  law 
of  associated  movements.  That  is,  if  the  right  eye  devi- 
ates up  behind  the  screen  when  the  left  eye  is  fixing,  the 
latter  will,  when  the  screen  is  shifted  so  as  to  cover  it, 
move  down  in  company  with   the   right,  which   now,  being 


90  NEW  CLASSIFICATION  OF  MOTOR  ANOMALIES. 

uncovered,  is  descending  in  order  to  get  into  the  position 
of  fixation.  In  certain  remarkable  cases,  however,  the 
deviafion  of  both  eyes  is  up  (  aiKitropia  ),  or  of  both  eyes  is 
down  (catatropia  )  behind  the  screen.  That  is,  if  the  right 
eye  deviates  up  behind  the  screen  when  the  left  is  fixing, 
the  latter,  as  soon  as  the  screen  is  shifted  and  the  right  eye 
moves  down  to  get  into  the  fixing  position,  will  move  up. 
In  this  case  the  visual  lines,  instead  of  remaining  at  a  con- 
stant angle,  as  in  the  case  before  cited,  will  approximate 
until  they  become  parallel,  and  will  then  diverge  in  the  op- 
posite direction. 

Stevens  (Ainiales  (VornUstiqi(e,  CXIII.,  3,  April,  1895,) 
was  the  first  to  carefully  study  these  cases  and  call  them 
by  the  names  above  given.  ^  His  view  of  them  is  that  they 
are  due  to  the  fact  that  initial  elevation  or  initial  depres- 
sion of  both  visual  lines  (  i.  e.,  an  excessive  sursumversion 
or  deorsumversion)  is,  in  these  anomalous  cases,  the  nat- 
ural state,  to. which  each  eye  tends  to  return  when  not 
used  for  vision.  But  the  condition  may  also,  and  perhaps 
more  plausibly,  be  ascribed  to  a  spasm  of  sursumvergence, 
or  rather  of  the  action  opposed  to  sursumvergence  (that, 
namely,  by  which  the  visual  lines,  when  vertically  di- 
verged, are  brought  together  again). 


X. 

ANOMALIES  OF  ROTATION-MOVEMENTS. 

Anomalous  conditions,  in  which  divergence  or  converg- 
ence of  the  vertical  meridians  of  the  two  corneae  (other  than 
the  physiological  divergence  which  occurs  when  the  visual 
lines  are  converged)  have  been  described  by  Savage.  His 
views,  however,  although  urged  with  much  plausibility,  are 
still  far  from  being  demonstrated.  It  seems  likely  that 
these  conditions,  if  they  exist  at  all.  are  rare  and  of  com- 
paratively little  significance. 

•SclnveiKfrer,  to  hv  sure  (Arrh.  f.  A  Hgenlicilk.,  XXIV.,  :i-4,  1894), 
nuMitioiis  sucli  a  case,  l)Ut  witlmiit  atrfini)tin.<r  any  explanation  of  the 
pliciioiiicnon. 


NEW  CLASSIFICATION  OF  MOTOR  ANOMALIES.  91 

XI. 

RECAPITULATION. 

The  conditions  that  I  have  sketched  embrace  all  the  dif- 
ferent deviations,  both  manifest  and  latent,  that  are  usu- 
ally described.  As  the  system  of  classification  here  pro- 
posed differs  radically  from  that  generally  employed,  it 
may  be  well,  in  a  brief  recapitulation,  to  show  the  points  of 
contact  between  the  two. 

The  ordinary  classification  divides  deviations  into  Out- 
ward (or  divergent).  Inward  (or  convergent),  and  Vertical 
(upward  or  downward). 

These  deviations  may  be  due  to  the  following  causes: 

SUMMARY   OF   DEVIATIONS. 

I.  Inward  Deviations  (Esophoria,  Convergent  Strabis- 
mus) may  be  due  to : 

a.  Over-action  of  one  or  both  internal  recti  or  of  the 
other  adductors  of  the  eye  (superior  and  inferior  recti). 

h.  Under-action  of  the  external  rectus  or  of  the  other 
abductors  (the  obliques). 

<•.  Under-action  of  the  center  for  producing  divergence 
movements  (divergence -insufficiency). 

d.  Over-action  of  the  center  for  producing  convergence 
movements  (convergence-excess,  which,  in  turn,  may  or 
may  not  be  due  to  excessive  accommodative  action). 

e.  Two  or  more  of  the  above  causes  combined. 

II.  Outward  Deviations  (Exophoria,  Divergent  Strabis- 
mus) may  be  due  to: 

a.  Under-action  of  the  internal  rectus  or  of  the  other 
adductors  (superior  and  inferior  recti). 

h.  Over-action  of  the  external  rectus  or  of  the  obliques. 

c.  Under-action  of  the  center  for  producing  convergence 
movements  (convergence-insufficiency,  which,  in  turn, 
may  or  may  not  be  due  to  insufficiency  of  accommodative 
action.) 


92  NEW  CLASSIFICATION  OF  MOTOR  ANOMALIES. 

f/.  Over-action  of  the  center  for  producing  divergence 
movements  (divergence-excess). 

p.  Two  or  more  of  the  above' causes  combined. 

III.  Upward  and  Downward  Deviations  (Hyperphoria, 
Strabismus  Sursumvergens  and  Deorsumvergens)  maybe 
due  to: 

a.  Over-action  of  an  elevator  or  depressor  muscle. 

h.  Under-action  of  an  elevator  or  depressor  muscle. 

r.  Both  of  the  above  causes  combined. 

d.  Sursumvergence- spasm,  either  uncomplicated  or  com- 
bined with  under-action  or  over-action  of  an  elevator  or 
depressor. 

IV.  Mixed  Forms  (Hyperphoria  combined  with  Exopho- 
ria,  Hyperphoria  combined  with  Esophoria,  and  Esophoria 
in  one  part  of  the  field  of  view  combined  with  Exophoria  in 
another)  are  frequent. 

The  differeiifiafion  of  these  separate  groups  included  un- 
der the  above  general  heads  is  readily  made,  for  all  have 
well-marked  signs  which  are  detailed  in  the  foregoing 
sections  (V.-VHI.).  The  diagnosis,  indeed,  can  in  almost 
every  case  be  made  at  once  by  applying  the  three  broad 
principles  laid  down  in  Section  IV.  (at  the  end  of  the  re- 
marks upon  comitant  and  non-comitant  deviations). 

The  liagnostic  points  indicative  of  the  chief  conditions 
met  with  are  recapitulated  in  the  following  table. 

DIAGNOSTIC  TABLE— TERMS  EMPLOYED. 

/*(■  (convergence  near-point),  the  distance  of  the  near- 
point  of  convergence  from  the  bridge  of  the  nose,  when 
the  object  of  fixation  is  carried  toward  the  eyes  in  the  me- 
dian line. 

/V  (  Jl ),  the  distance  of  the  near-point  of  convergence 
from  the  bridge  of  the  nose  when  the  object  of  fixation  is 
carried  directly  toward  the  patient's  left  eye  from  some 
point  situated  to  the  front  and  riuht  of  him  (see  Fig.  8  and 
accompanying  explanation).  Pc  (K)  will,  in  this  case, 
denote  the  point  at  which   the  right  eye  sags  off  in   eon- 


NEW  CLASSIFICATION  OF  MOTOR  ANOMALIKS-  93 

vergence.  Similarly,  /V(  L  )  denotes  the  point  at  which  the 
left  eye  ceases  to  converge  when  the  object  is  carried  from 
the  left  side  directly  toward  the  right  eye. 

Convergence-addnctiou,  the  power  possessed  by  either 
eye  of  moving  inward  in  response  to  a  convergence-stim- 
ulus.    Its  measure  is  the  Pc. 

Associated  adduction,  the  power  possessed  by  either  eye 
of  moving  inward  in  performing  associated  parallel  move- 
ments, /.  e.,  when  the  other  eye  is  moving  outward.  It  is 
regularly  greater  than  the  convergence-adduction. 

Priioti-convergence  (the  adduction  of  most)  is  the  ability 
to  converge  the  eyes,  when  overcoming   prisms,  base  out. 

PfisD) -divergence  {i\ie  SihdiMction  of  most  authors)  is  the 
ability  to  diverge  the  eyes  as  measured  by  the  degree  of 
prism,  base  in,  which  the  eyes  can  overcome.  This  is  said  to 
be  i>roportionate  to  the  amount  of  an  exophoria  or  esophoria 
when  it  equals  7  -f  the  exophoria  or  7  — the  esophoria 
(for  distance). 

A.       OUTWARD      OR     DIVERGENT     DEVIATIONS. —  (EXOPHORIA, 
DIVERGENT     SQUINT.) 

I.  Deviation  and  its  evidences  (exophoria,  crossed  di- 
plopia) noticeably  greater  in  some  directions  of  the  gaze 
than  in  others.  Pc  abnormally  remote.  Pc  (R)  greater 
or  less  than  Pc  and  still  more  so  than  Pc  (L).  Excursion  of 
one  eye  and  its  field  of  fixation  abnormally  increased  or  re- 
duced in  some  one  direction,  both  for  distance  and  near. 
Under=Action  of  an  Adductor  or  Over=Action  of  an  Abduc= 
tor  riuscle. 

Note— The  diagnosis  as  to  whether  it  is  uuder-action  or  over- 
action  that  is  present  may  be  made  from  the  points  detailed 
under  the  head  of  diagnosis  (4)  in  Section  V. ;  and  the  sped  He 
diagnosis  of  the  muscle  affected  maybe  made  from  the  tables 
of  diplopia  in  same  section  ((i).  As  there  stated,  a  crossed 
diplopia  (or  an  exophoria)  which  increases  as  the  eyes  are 
carried  to  the  right  indicates  weakness  of  some  muscle  of  the 
left  eye  or  over-action  of  some  muscle  of  the  right  eye;  and 
any  exophoria  which  changes  markedly  in  degree  as  the  e>es 
are  shifted  can  be  due  only  to  under-action  f)f  an  interims  or 
over-action  of  an  externus. 

II.  Deviation  and  its  evidences  (exophoria,  crossed  di- 


94  NEW  CLASSIFICATION  OF  MOTOR  ANOMALIES. 

plopia)  sensibly  the  same  in  all  directions  of  the  gaze. 
Pc  (R)  equals  Pc  (L).  Excursion  of  both  eyes  and  their 
fields  of  fixation  normal  (at  least  for  distance). 

(II.)     Deviation  or  exophoria  sliprht  for  distaiici-.     Marked  for  near 
l)y  all   tests.     Pc  abnormally  remote,     ronvergenee-adtliu-tion 
less  than  associated  adduction  (Graefe's  test— see  Section  VI.). 
Prism-diverg:ence  not  specially  Ki'<"at  (usually  8-10'^.  or  may  be 
subnormal).     Prism-converuvnce   subnormal  and  effected  with 
ditficulty.     Convergence-lnsufficency. 
Note. — The  diagnosis  between  an  iicconiinoddtire  and  a  nou-nc- 
commodative  convergence-insufficiency  will  be  made  by  refer- 
ence to  the  etiology  (see  Section  VI.)  and  by  observing  the 
effect  of  glasses.     The   latter,   if  suitably  adjusted,  usually 
relieve  a  trouble  of  purely  accommodative  origin. 
(h.)     Exophoria  marked  for  distance;  less  for  near  (relations  for 
near  may  be  nearly  normal) .     Pc  normal,  or  nearly  so.     Prism- 
divergence  large  (in  typical   cases  disproportionately  so:   /.  e., 
it  is  greater  than  7°  -f  the  exophoria  for  distance).     Prism- 
convergence  often  normal  and  effected  with  facility.     Diverg- 
ence-Excess. 
(c.)     Exophoria  marked  for  both  distance  and  near.     Pc  abnor- 
mally remote.       Convergence-adduction  less  than  associated 
adduction  (Graefe's  test— see  Section  VI.).     Prism-divergence 
large,  but  not  disproportionately  so,  compared  with  the  amount 
of    exophoria.       Prism-convergence    usually    reduced  — often 
greatly.      Divergence-Excess    with    Convergence-Insuffi- 
ciency. 
Note.— The  determination  as  to  whether   the  divergence-excess 
is  secondary  to  the  convergence-insufficiency,  or  is  primary, 
may  be  nuule  by  the  differential  diagnosis  given  in  Section  VII. 
This    condition    is    not  always  easy  to  diagnosticate  from  a 
comitant  deviation  produced  by  under-action  of  one  or  both 
interni,   combined    with    over-action    (due    to  compensatory 
contraction)  of  the  ejiterni.     Moreover,  it  is  not  improbal)le 
that    a  long-continued  divergence-excess  may  give  rise   not 
only  to    an    insufficiency  of  ccmvergence,  but  to  a  weakness 
of  the  interni  j>cr  se,  due  to   their  protracted  inaction  and  to 
the  unfavorable  conditions  under  which  they  work. 
(d.)     Exophoria  marked  for  distance.     For  near,  slight  exophoria. 
orthophoria,  or  esophoria.     Pc    normal    or   excessively    near. 
Convergence-adduction      greater    than     associated  adduction. 
Prism-divergence      large,     sonu'times     dispropin-tionately     so. 
Prism-convergence  normal  and  readily  ctt'ected.     Divergence- 
Excess  with  Convergence-Excess. 
XoTE.— Tliesecases  are  sometitiics  difficult  to  diagnosticatt'  fn.m 


NEW  CLASSIFICATION  OF  MOTOR  ANOMALIES.  95 

those  of  anatomical   pivpoiuli'i-auce  of  Itoth   externi  (struct- 
ural deviation),  combined  with  a  convergence-excess. 
The  convergence-excess  in  these  cases,  being  often  accommoda- 
tive, will   frequently  disappear  upon  the  use  of  the  proper 
glasses. 
(e.)  Convergence-Insufficency  with  Divergence-Insufficiency. 
(See  Inward  Deviations,   B.  II.,  d.) 

III.  Mixed  conditions,  in  which  the  deviation  increases 
more  or  less  in  certain  directions  of  the  gaze,  but  in  which 
the  phenomena  noted  under  II.  are  likewise  present 
(combination  of  over-action  or  under-action  of  muscles 
with  a  divergence-excess  or  a  convergence-insufficiency) ; 
and  conditions  in  which,  by  the  weakness  of  some  muscles 
and  the  over-action  of  others,  a  comitant  exophoria  or 
divergent  squint  has  been  established,  are  not  readily  ana- 
lyzed into  their  constituent  factors. 

B.      INWARD  OR  CONVERGENT  DEVIATIONS — (eSOPHORIA,  CON- 
VERGENT squint)  . 

I.  Deviation  and  its  evidences  (esophoria,  homonymous 
diplopia) ,  noticeably  greater  in  some  directions  of  the  gaze 
than  in  others.  Pc  abnormally  near.  Pc(R)  greater  or 
less  than  Pc  and  still  more  so  than  Pc(L).  Excursion  of 
one  eye  and  its  field  of  fixation  abnormally  increased  or 
reduced  in  some  one  direction,  both  for  distance  and  near. 
Under=Action  of  an  Abductor  or  Over=Action  of  an  Adduct- 
or Muscle. 

Note. — For  the  specific  differentiation  see  Section  V.,  remarks 
on  diagnosis,  (4)  and  (G).  As  there  stated,  a  homonymous 
diplopia  (or  an  esophoria)  which  increases  as  the  eyes  are 
carried  to  the  right,  indicates  weakness  of  some  muscle  of 
the  right  eye  or  over-action  of  some  muscle  of  the  left  eye ; 
and  an  esophoria  which  changes  markedly  in  degree  as  the 
eyes  are  shifted  can  be  due  only  to  under-action  of  an  ex- 
ternus  or  over-action  of  an  internus. 

II.  Deviation  and  its  evidences  (esophoria,  homonymous 
diplopia)  sensibly  the  same  in  all  directions  of  the  gaze. 
Pc(R)  equals  Pc(L).  Excursions  of  both  eyes  and  their 
fields  of  fixation  normal  (at  least  for  distance). 

(a.)     Esophoria  marked  for  distance:     slight  or   replaced  by  ex- 
ophoria for  near.     Pc  normal.     Convergence-adduction  equal 


96  NEW  CLASSIFICATION  OF  MOTOR  ANOMALIES. 

ti>  oi-  iiKnc  ()!•  less  tliaii  tlic  associated  adduction.  l*rism-di- 
\('ry-ciic('  low  (may  l)c  disitroportioiiatcly  so.  /.  v..  is  less  than 
7  — the  esoi)horia  for  distain-e).  l'i'isiii-coiiver»i-encc  iioniial, 
or  often  suhiiornial.     Divergence-Insufficiency. 

(h.)  E.soplioria  slifrht  for  distance :  more  for  near.  Pc  exces- 
.sively  near  (less  than  1  inch).  Converjarence-adduction  may  be 
greater  than  associated-adduction.  I'rism-diverg:ence  ncn-mal, 
or  Init  slijriitly  sul)nornial  (never  disproportionately  low). 
Prism-con verufence  normal.     Convergence-Excess. 

Note. — The  diagfiiosis  between  an  incDiiniKKtattn-  and  ;i  non-ac- 
cuiinnodntire  convergence-excess  will  be  made  by  refei'ence 
to  the  etiology  (see  Section  VI.)  and  by  observing  the 
eltect  of  the  long-continued  use  of  glasses  (or  of  atropine), 
which  in  most  cases  will  relieve  a  difiieulty  of  purely  accom- 
modative origin. 

(c.)  Esophoria  marked  for  distance  and  near.  Pc  excessively 
near.  Convergence-adduction  e(juals  oris  greater  than  asso- 
ciated adduction.  Prism-convergence  low  in  proportion  to 
degree  of  esoi)horia  for  distance,  or  disproportionately  low. 
Prism-convi-rgence  normal.  Divergence-Insufficiency  and 
Convergence-Excess. 

NoTK. — The  determination  as  to  whether  the  divergence-insuf- 
ticiency  is  secondary  to  the  convei-gence-excess,or  is  primary, 
maybcmade  from  the  dift'erential  diagnosis  in  Section  VII. 

{(I.)  Esophoria  marked  for  distance;  exophoria  (of  mon-  than  4 
or  5°)  for  near,  noticeable  by  all  tests.  Pc  abnormally  remote. 
Convergence-adduction  less  than  associated  adduction.  Prism- 
convergence  low.  Prism-convergenci'  sul)normal  ami  hainl  to 
tram.  Divergence-Insufficiency  with  Convergence-Insuf- 
ficiency. 

(e.)     ( 'on  rnycnce- J-'Jjvess  irith  J)i rcn/cii cc- K.rccss . 
(See  Outward  Deviation,  A.  II.,  d). 

IIL  Mixed  conditions,   analogous  to  those  given   under 
Outward  Deviations  III.  exist,  but  are  hard  to  analyze. 

C.      VERTICAL  DEVIATIONS — (HYPERPHORIA,  STRABISMUS  SUR- 
SUMVERGENS  AND  DEORSUMVERGENS.) 

I.  Hyperphoria  or  its  evidences  (vertical    diplojiia)  in- 
creasing in  some  one  direction  of  the  gaze. 

((I.)     Hyp«'ii.h(.ria    increasing    as    the    i-ycs    arc   carrictl    upward. 

Over-Action  or  Under-Action  of  an  Elevator  IMuscle. 
(h.)     llyi»eri»horia  increasing  as  the  eyes   are  carried  downward. 

Over-Action  or  Under-Action  of  a  Depressor  Muscle. 


NEW  CLASSIFICATION  OF  MOTOR  ANOMALIES.  97 

NoTK.— F'or    tlic    spccilic    diafiiiosis    of  the   imisclc   anVctcd  see 
Section  V.,  remarks  on  diagnosis  (4  and  0). 
II.  Hyperphoria  the  same  in  all  parts  of  the  field  (com- 
itant  hyperphoria,  comitant  vertical  strabismus). 

(a.)  Due  proI)a))ly  in  most  eases  to  under-action  of  an  elevator  or 
depressor,  with  over-action  of  on*'  or  more  antafj-onislic  mnscle. 
Mixed  Cases. 

(b.)  Sometimes  to  equal  \ertieal  diver>;enee  of  the  visual  lines 
(see  Section  VIII).     Sursumvergence-Excess. 

CONCLUSION. 

One  who  proposes  a  new  classification  must  be  pre- 
pared to  defend  his  position  by  showing  that  it  subserves 
some  useful  purpose.  That  this  is  the  case  with  the  one 
propounded  in  the  preceding  pages  seems  to  me  proved  by 
the  following  reasons : 

1.  The  classification  is  based  upon  physiological  facts 
instead  of  mere  external  appearances. 

2.  Its  divisions  correspond  to  natural  groups,  distinct  in 
nature  and  symptoms,  and  frequently  requiring  widely 
different  methods  of  treatment. 

3.  The  groups  so  made  are  readily  distinguishable  in 
practice  by  the  signs  they  afford. 

4.  We  can  by  means  of  the  scheme  here  presented  ana- 
lyze the  frequently  occurring  mixed  forms,  and  from  our 
knowledge  of  the  nature  and  tendency  of  the  component 
lesions  determine  to  which  of  the  latter  our  treatment  shall 
be  addressed. 


INDEX. 


Abducting  power  of  the  obliques  and 
external  rectus,  auionnt  of.  It,  15. 

Alxluction  (in  proper  sense  of  term, 
licnolini;  the  power  possessed  by  each 
eye  of  moving  outward),  9. 

Abduction  (in  its  ordinary  sense  of  mut- 
ual divergence  of  the  visual  lines). 
See  Divergence  and  Prism- Dioerf/eiice. 

Accommodation  always  brought  into 
play  when  convergence  is  exercised  by 
prisms,  Jl:  this  shoi-.ld  be  taken  into 
account  in  making  muscular  tests,  .'^S. 

Acct)mmodative  convergence-excess,  79. 

.-Accommodative  converg  e  n  c  e  -  i  n  s  u  ffi- 
cieucy,  73. 

.Adductiug  power  of  the  superior,  infe- 
rior, and  internal  recti,  amount  of, 
14,  15. 

Adduction  (in  proper  sense  of  term, 
denoting  the  power  possessed  by  each 
eye  of  moving  inward),  9;  varieties 
(convergence  -  adduction,  associated 
adduction),  93. 

Adduction  (in  its  usual  sense  of  mutual 
convergence  of  the  two  visual  lines). 
Sec  Concergence  and  Pritmconcer- 
genre. 

.•\natropia,  6S,  9U. 

Antagonists,  associated,  19, 2U,  29. 

Antagonists,  direct,  7. 

Associated  adduction,  93. 

Associated  antagonists,  19,  20,  29. 

Associated  convergent  movements,  tests 
for,  36.  ,  ,       , 

As.sociated  parallel  movements,  table  of, 
1719;  extent  of,  20;  centers  for,  22; 
tests  for,  35;  anomalies  of,  67. 

Association  centers.  22. 

Asthenic  exophoria.  77. 

Asthenic  vertical  orthophoria.  6s. 

B. 

Binocular  fixation,  field  of,  2u;  tests  for, 

.3U,  35. 
Binocular  single  vision,  field  of,  2C;  tests 

of,  .35. 

c. 

Catalropia,  6K,  90.  . 

Choreiform  spasm  of  associated obliciue 
movements,  69. 

Clissification  of  ocular  deviations,  upon 
what  based,  42,  43;  author's  pro- 
posed scheme,  44;  previ.iiis  scl;<  lues,  1. 

Comitant  and  non-coiin(;int  (l.Mations, 
^6etseci.;  laws  govtrnmi;  U.in-lnrma- 
tion  of,  4H;  character  ..1  -rm  ii  nu)ve- 
ments  in,  .33. 

Comitant  hyperphoria.  60.9/ . 

Compensation  of  deviations,  law  ot,  4h, 

Concomitant.    See  Comitant. 
Congenital  deviations,  characters  ol   bh. 
Constant  squint,  44. 
Convergence,  exercise  ol  by  prisms,   -J; 


exercise  of,  produces  sjjasm  of  accom- 
modation, 24,  3S;  maximum  i>ower  of, 
22 ;  test  for,  .36. 

Convergence-adduction,  93. 

Convergence-anomalies,  71. 

Convergence-e.vcess.  7S;  differential  di- 
agnosis of,  96;  with  secondary  diver- 
gence-insufficiency, diagnosis  of,  S4,  96. 

Convergence-insufficiency,  72;  charac- 
ters, 72;  non-accommodative,  73;  ac- 
commodative, 75;  course.  75;  compli- 
cations, 77.  <S7.  94;  symptoms.  77, 
diagnosis,  S7,  94;  treatment,  77. 

Convergence-movements,  22. 

Convergence  near-point,  22,  92;  determi- 
nation of,  .16. 

Convergence-paralysis,  71. 

Convergence-spasm.  3S,  7.s. 

Convergence  of  the  vertical  meridians  of 
the  corner,  26;  abnormal,  90. 

Crossed  diplopia,  31. 

Crossed  parallax.  34. 

D. 

Deorsumduction  (in  proper  sense  of 
term),  10. 

Deorsumversiori,  how  effected,  IS;  par- 
alysis of,  6S. 

Depressing  power  of  inferior  rectus  and 
superior  oi)lique.  amount  of,  14. 

Deviations,  classification  of,  1,  42-46;  di- 
agnostic table  of,  92;  inward,  91,  95; 
mixed  forms,  92,  95,  96.  97;  outward,  91, 
63-95:  transformation  and  evolution  of 
law  of.  48,  49;  vertical,  92,  96. 

Dextroversion,  how  effected,  17;  par- 
alysis of,  67;  spasm  of,  6.S. 

Diagnostic  table  of  deviations,  92;  of 
muscular  paresis  and  spasm  based  on 
the  double  images,  61-63. 

Diplopia,  how  brought  out  and  differen- 
tiated. 31;  how  measured,  31;  method 
of  recording,  39;  transient,  indicating 
physiological  limitation^of  field  of 
single  vision,  35;  varieties  (crosse<l, 
left,  homonymous,  right,  etc.),  .^0,  31; 
table  of,  in  muscular  paralysis  and 
spasm,  61-63. 

Diplopia-test,  30,  35,  36,  .W. 

Divergence  (or  Diverging  power).  24; 
nature  of.  25;  produced  by  pri.sms.  24. 
.3S;  of  slight  amount,  physiological  for 
near  points.  36;  tests  for.  .^S. 

Divergence-excess,  S6, 94. 

Divergence-insufficiency.  S3.  96. 

Divergence  of  the  vertical  meridians  of 
the  cornea;,  27;  pathological.  90. 

Donders'  lawdiagramatically  illustrated. 

Downward   associated  movements.     See 

Deormmveruon. 
Downward  deviations,  92,  96. 
Dynamic  association-tests,  .Ui. 
Dynamic  disassociation-tesls,  .30. 


I'Uectricity,  <►). 
Klevating  power  of 


INDEX. 


99 


inferior  oblique,  amount  of,  It. 

Kquilibrium  test,  .n,  ,1S,  36,  .V). 

Ksophoria,  3J;  accommodative.  79, 
sthenic,  79;  varieties  of,  according  to 
the  new  classification,  91;  varieties  of, 
how  differentiated,  95. 

Kxophoria,  3.';  asthenic,  77;  varieties  of. 
according  to  the  new  classification,  91 ; 
varieties  of,  how  differentiated,  93-95. 

Kxteraal  rectus,  action  of.  6,  9-11.  17-19; 
action  of,  how  modified  by  the  verti- 
cally acting  muscles,  2s. 
F. 

Field  of  binocular  fi.Yation.  Ju. 

Field  of  binocular  single  vision,  2u;  con- 
centric contraction  of.  3S.  59;  how 
mapped  out.  ,^5,  39;  pathological  and 
accidental  limitation  of,  as  shown  by 
the  varieties  of  diplopia  occurring,  35; 
physiological  limitation  of.  35. 

Field  of  (monocular)  fixation,  12,  40; 
diagram  of.  26.  27;.  how  limited  in 
muscular  paralysis,  29.  59;  how  map- 
ped out,  35;  measurements  of.  12.  13. 

Fixation-test,  30,  35,  .36. 

Fixing    eye,  how  to  determine  the.  3?!. 

Fusion  near-point.  See  Convergence 
near-point. 

H. 

Heteronymous  diplopia,  31. 

Heteronymous  parallax,  3-t. 

Heterophoria.  3,  43;  insertional.  51; 
spastic.  60;  structural,  51. 

Heterotropia.  3,  44. 

Homonymous  diplopia,  3li. 

Homonymous  parallax.  34. 

Hyperkineses,  44. 

Hyperphoria,  31,  59;  comitant,  60,  97: 
varieties  of,  classified  according  to 
external  character,  S9;  varieties  of. 
classified  according  to  etiology.  92; 
varieties  of,  how  differentiated,  96. 

Hypertropia,  89.  .See  also  Strabtsnms 
sursumverffens  and  Struhismus  deorsum- 
vergens. 

Hypokineses.  43. 

I. 

Individual  muscles,  actions  of.  6;  an- 
omalies of.  49;  slight  cases  of  anomal- 
ies of,  59. 

Inferior  oblique,  action  of.  6.  9-11,  17-19; 
field  of  action  of,  graphically  shown, 
26;  and  superior  oblique,  combined  ac- 
tion of,  28;  and  superior  rectus,  com- 
bined action  of.  26,  27. 

Inferior  rectus,  action  of,  6,  9-11,  17-19; 
field  of  action  of,  graphically  shown. 
27;  and  superior  oblique,  combined 
action  of,  27;  and  superior  rectus, 
combined  action  of,  27. 

Inspection,  30,  35,  36,  39. 

Insufficiency.discoveryof,  3;  faulty  use  of 
term,  3.     See  also  Heterophoria. 

Intermittent  squint, 44. 

Internal  rectus,  action  of.  6,  9-11,  17-19; 
action  of,  how  modified  by  that  of  the 
vertical  muscles,  28. 

Innervational  deviations.  52. 
Insertional   squint   or    heterophoria.  49, 

51. 
Inward  deviations,  varieties  of,  classified 
according    to    etiology,    91;    varieties, 
differential  diagnosis  of,  95. 
L. 

Latent  squint,  44. 

Law  of  comitance,  4S,  49. 


Left  associated  movements.  .See  Sinis- 
irorersion. 

Left  diplopia.  31. 

Left  parallax.  31. 

Left  sursumvergence.  38. 

Listing's  law,  diagrammaticallv  illus- 
trated, 29. 

M. 

Maddox  rod.  31  (note). 

Manifest  sciuint.  44. 

Mixed  forms  of  deviation,  92,  95,  96,  97. 

-Mixed  nystagmus.  70. 

Movements,  binocular,  five  classes  of, 
15,  16;  with  unimportant  exceptions 
subserve  binocular  fi.xation,  15;  de- 
scription of,  17-29. 

Movements,  monocular,  7-14;  extent  of, 
11 ;  can  be  performed  in  all  directions, 
8;  tabular  view  of,  9-11;  diagrammatic 
representation  of,  26-29. 

Movement  of  redress,  33. 

Muscles  of  eye.  combined  actions  of.  27, 
2.S;  table  of  action  of,  6. 

N. 

Near-point  of  convergence,  22,  92;  de- 
termination of.  36. 

Nerve-centers  governing  individual  ocu- 
lar muscles,  S;  for  associated  parallel 
movememnts.  22;  for  movements  of 
convergence,  22. 

Neurasthenia,  enfeebled  action  of  eve- 
muscles  in,  59. 

Non-accommodative  convergence  -  ex- 
cess, 79. 

Non-accommodative  convergence-insuf- 
ficiency, 73. 

Nou-comitant  deviations,  46  et  seq. , 
character  of  screen-movement  in,  33. 

Nystagmus,  bilateral  (or  ordinary),  69; 
unilateral,  67. 

o. 

Obliques,  combined  action  of,  28. 

Operation  in  cases  of  convergence-ex 
cess,  S3;  in  convergence-insufficiency, 
78;  in  divergence-excess,  88;  in  diver- 
gence-insufficiency, 86;  in  muscular 
paresis  or  spasm,  64-66. 

Outward  deviations,  varieties  of,  classed 
according  to  etiology,  91;  varieties  of, 
differential  diagnosis,  93-95. 

Over-action  and  underaction,  differential 
diagnosis  of,  59. 

P. 

ranaroma-asthenopia.  Panorama  head- 
ache, 85. 

Parakineses,  44. 

Parallax,  34;  measurement  of,  .VS.  36,  39; 
varieties.  35. 

Parallel  squint.  71. 

Paralysis  of  associated  parallel  move- 
ments, 67 

Paralysis  of  convergence,  71. 

Paralysis  of  ocular  muscles.  49.  52-67; 
differentiation  of,  from  spasm,  58;  diag- 
nosis of,  by  means  of  double  images. 
til-63;  limitation  of  field  of  fixation  and 
character  of  diplopia  in.  graphically 
represented.  29. 

Paretic  esophoria.  95. 

Paretic  exophoria,  93. 

I'aretic  hyperphoria.  96. 

Paretic  squint.  See  I'urali/sis  of  ocular 
nutacien. 

Periodic  squint.  44. 

Phorometer,  ?,2. 

Prisms,  seldom  giving  precise  measure- 


100 


INDEX. 


iiient  of  (lijilopia,  31  (note);  when  used 
as  an  exercise.  Kivin^  Kood  results  in 
converKence-insufficiency.  7K.  hut  of  no 
avail  in  converKence  excess  or  diver- 
trence-insiifficiency,  S3,  S5;  when  em- 
p'.oyed  for  constant  wear,  sonulinics 
serviceable  in  anomalies  of  the  indi- 
vidual iniiscles  and  particularly  in 
vertical  deviations.  64,  but  niiscliiev- 
ous  in  convergence-insufficiency,  .on- 
vergence  -  excess,  and  divergence- 
insufficiency.  78,  «3,  85. 

Prism-convergence,  23,  39.  89. 

I'rism-divergence,  24,  38,  39,  93. 

Pseudo-esophoria,  79. 

R. 


"Relaxation"  of  the  muscles  often  really 
a  condition  of  active  contraction,  2^. 

Right  as.sociated  movements.  ,See  Ocx 
irorersioii. 

Right  diplopia,  31. 

Right  hyperphoria,  31. 

Right  parallax.  ,34. 

Right  sursumvergence.  38. 

Rotation  movement.s.  .See  TorsU  ii  - 
movements. 

s. 

Screen-test,  3.',  35,  .36,  39. 

Sinistroversion,  how  effected,  17;  paraly- 
sis of,  67;  spasm  of.  68. 

Spa.sm  of  associated  parallel  movements. 
68. 

Spasm  of  convergence,  78. 

Spasm  of  ocular  mnscles,  52-55;  diag- 
nosticated from  paralysis,  58;  slight 
cases  of,  59;  diagnosis  of.  by  means  of 
double  images,  61-63;  treatment,  6,3-67. 

Sp.Tstic  esophoria,  95. 

.Spastic  exophoria,  93. 

Spastic  heterophoria,  fin. 

Spastic  hyperphoria,  96 

Spastic  squint.  See  Sptiniii  of  ontUir 
muxcles. 

.Static  tests.  MK 

Stevens'  classification.  .^:  phorunielev, 
32;  sphere,  31  (note):  theory  (jf  ana- 
tropia  and  catatropia,  9ii, 

Sthenic  esophoria,  79. 

-Strabismus  accommodative.  79;  con- 
stant, 44. 

Strabismus  convergeus,  varieties  of. 
classed  according  to  etiologj',  91 ; 
varieties  of,  how  differentiated,  95. 

Strabismus  deorsumvergens,  5,  7,  89,  8.'; 
varieties  of.  how  differentiated.  96. 

Strabismus  divergens,  varieties  of,  ac- 
cording to  etiology,  91;  varieties  of, 
how  differentiated,  93-95. 

.Strabismus,  innervational,  5-';  intermit- 
tent, 44;  latent,  44;  manifest,  44;  mus- 
cular, .50;  parallel  71;  paretic  (see 
I'arnhjsis  of  omliir  mnxcli'S) ;  periodic. 
II;  spastic  I  see  Spa.im  of  ocular  ^mus- 
clen)  ■  strucl\iral.  l'i-51. 

StrabTsmiis  sursumvergens.  57,  89,  92; 
varieties  of,  how  differentiated,  %. 

Structural  squint  and  heterophoria,  49- 
51. 

Strychnine,  6-1. 

Superior  obliciue,  action  of,  6,  9-11,  17-1''; 
field  of  iiction  graphically  shown,  26; 
;in<l  inferior  oblique,  combined  action 
of,  28:  a'nd  inferior  rectus,  combined 
action  of,  27. 


.Superior  rectus,  action  of.  «'. 'i-ll.  17  1'^; 
field  of  action  of.  graphically  shown. 
26;  and  inferior  oblique,  combined  ac- 
tion of,  26.  27;  and  inferior  rectus, 
combined  action  of.  27. 

Sursumduction  (in  proper  sense  of  term, 
uuaning  absolute  movement  of  eye 
upward).  lU. 

Sursumduction  (in  ordinary  sense  of 
term,  meaning  vertical  divergence 
of  the  visnaUlines).'  .See -Awrsimrer- 
geme. 

Sursumvergence.  26;  anomalies  of.  8s; 
tests  for.  3s. 

.Sursumvergetice-excess.  88.  97. 

Sursumvergcnce-insufficiency.  88. 

Sursumversiou,  how  effected.  17;  para- 
lysis of.  68. 

Swivel-movements.  See  Tursioii  move 
iiients. 

T. 


Table  of  actions  of  individual  muscles,  t: 

Table  of  associated  antagonists.  20. 

Table  of  associated  parallel  movements. 
17-19. 

Table  of  deviations  classed  according  to 
etiology.  44-46. 

Table  of  deviations  classed  in  the  usual 
way  as  outward,  inward,  and  vertical, 
with  the  etiological  diagnosis  of  each 
variety,  92-97. 

Table  of  diplopia  in  muscular  paresis 
and  spasm.  61-63. 

Table  of  the  movements  of  each  eye  and 
of  the  part  that  the  different  muscles 
take  in  producing  them,  9-11. 

Tests.  .^O-^O:  of  associated  convergent 
movements  36;  of  associated  parallel 
movements.  35;  for  binocular  fixation. 
30.  35;  of  binocular  single  vision.  .35: 
of  convergence.  36;  diplopia.  30.  35,  .36, 
.39;  of  divergence.  38;  equilibrium.  31. 
,35.  .36,  .39;  fixation,  .30.  .35.  .36;  inspec- 
tion, .30.  35.  .36.  .39;  parallax.  .34.  .39; 
phorometer,  31,  ,35.  .36,  ,39;  screen,  32. 
,'^5.  ,36.  .39;  static.  .30;  of  sursumverg- 
ence. .32.  40. 

Tonic  treatment.  64.7s. 

Torsion-movements  produced  by  indi- 
vidual muscles.  6;  produced  in  the  va- 
rious monocular  movements.  9-11 : 
produced  in  the  various  binocular 
movements.  17-19;  graphic  representa- 
tion of  individual  and  combined 
effects  of  the  muscles  upon.  2":  amount 
of,  how  determined.  14;  anomalies  of. 
90. 

u. 


->ocialed      movement.' 


See 


rpNMMil  iU\  iiitiuns.  varieties  of.  classed 
anonlini.;  I. .etiology.  89,  92;  varieties 
of,  liow  differentiated.  96. 

V. 

Vertical  deviations,  varieties  of.  classed 
according  to  etiology,  .89,  92:  varieties 
of.  how  differentiated,  %. 

Vertical  diplopia,  31. 

w. 

Work  done  by  the  different  mu.scle.s  in 
moving  the  eye.   l.v 


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